From 05b27ca729100ed5828f10d602a2480cc133f9c9 Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Tue, 26 Nov 2013 22:13:27 +0100
Subject: [PATCH 01/23] Tasks and unit tests for the streaming api hands-on;
 Change type of Person.birthdate to LocalDate - we do Java 8 ;-)

---
 .../de/codecentric/java8examples/Invoice.java | 28 ++++++++
 .../java8examples/InvoiceItem.java            | 28 ++++++++
 .../de/codecentric/java8examples/Person.java  | 36 ++++------
 .../lambdas/SpringJdbcSupportWithLambdas.java |  6 +-
 .../java8examples/streaming/Collecting.java   | 38 +++++++++++
 .../streaming/FilteringAndMapping.java        | 59 ++++++++++++++++
 .../codecentric/java8examples/TestData.java   | 36 ++++++++++
 .../codecentric/java8examples/TestUtil.java   | 27 --------
 .../lambdas/LambdaBasedComparatorTest.java    |  4 +-
 .../lambdas/LambdaExampleTest.java            |  4 +-
 .../streaming/FilteringAndMappingTest.java    | 68 +++++++++++++++++++
 .../java8examples/streaming/FlatMapTest.java  | 14 ++++
 .../streaming/StreamingApiTest.java           | 58 ----------------
 13 files changed, 291 insertions(+), 115 deletions(-)
 create mode 100644 src/main/java/de/codecentric/java8examples/Invoice.java
 create mode 100644 src/main/java/de/codecentric/java8examples/InvoiceItem.java
 create mode 100644 src/main/java/de/codecentric/java8examples/streaming/Collecting.java
 create mode 100644 src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
 create mode 100644 src/test/java/de/codecentric/java8examples/TestData.java
 delete mode 100644 src/test/java/de/codecentric/java8examples/TestUtil.java
 create mode 100644 src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java
 create mode 100644 src/test/java/de/codecentric/java8examples/streaming/FlatMapTest.java
 delete mode 100644 src/test/java/de/codecentric/java8examples/streaming/StreamingApiTest.java

diff --git a/src/main/java/de/codecentric/java8examples/Invoice.java b/src/main/java/de/codecentric/java8examples/Invoice.java
new file mode 100644
index 0000000..65e0418
--- /dev/null
+++ b/src/main/java/de/codecentric/java8examples/Invoice.java
@@ -0,0 +1,28 @@
+package de.codecentric.java8examples;
+
+import java.util.List;
+
+public class Invoice {
+
+    private String sender;
+    private String recipient;
+    private List<InvoiceItem> items;
+
+    public String getSender() {
+        return sender;
+    }
+
+    public String getRecipient() {
+        return recipient;
+    }
+
+    public List<InvoiceItem> getItems() {
+        return items;
+    }
+
+    public Invoice(String sender, String recipient, List<InvoiceItem> items) {
+        this.sender = sender;
+        this.recipient = recipient;
+        this.items = items;
+    }
+}
diff --git a/src/main/java/de/codecentric/java8examples/InvoiceItem.java b/src/main/java/de/codecentric/java8examples/InvoiceItem.java
new file mode 100644
index 0000000..44ed6a4
--- /dev/null
+++ b/src/main/java/de/codecentric/java8examples/InvoiceItem.java
@@ -0,0 +1,28 @@
+package de.codecentric.java8examples;
+
+import java.math.BigDecimal;
+
+public class InvoiceItem {
+
+    private String product;
+    private Integer quantity;
+    private BigDecimal pricePerUnit;
+
+    public String getProduct() {
+        return product;
+    }
+
+    public Integer getQuantity() {
+        return quantity;
+    }
+
+    public BigDecimal getPricePerUnit() {
+        return pricePerUnit;
+    }
+
+    public InvoiceItem(String product, Integer quantity, BigDecimal pricePerUnit) {
+        this.product = product;
+        this.quantity = quantity;
+        this.pricePerUnit = pricePerUnit;
+    }
+}
diff --git a/src/main/java/de/codecentric/java8examples/Person.java b/src/main/java/de/codecentric/java8examples/Person.java
index d2b3518..6cc8de8 100644
--- a/src/main/java/de/codecentric/java8examples/Person.java
+++ b/src/main/java/de/codecentric/java8examples/Person.java
@@ -1,7 +1,7 @@
 package de.codecentric.java8examples;
 
-import java.util.Calendar;
-import java.util.Date;
+import java.time.LocalDate;
+import java.time.Period;
 
 /**
  * A simple class that represents a person
@@ -12,27 +12,27 @@ public enum Gender {
         MALE, FEMALE
     }
 
-    private final String name;
+    private final String firstName;
     private final String lastName;
-    private final Date birthDay;
+    private final LocalDate birthDay;
     private Gender gender;
 
-    public Person(String name, String lastName, Date birthDay, Gender gender) {
-        this.name = name;
+    public Person(String firstname, String lastName, LocalDate birthDay, Gender gender) {
+        this.firstName = firstname;
         this.lastName = lastName;
         this.birthDay = birthDay;
         this.gender = gender;
     }
 
-    public String getName() {
-        return name;
+    public String getFirstName() {
+        return firstName;
     }
 
     public String getLastName() {
         return lastName;
     }
 
-    public Date getBirthDay() {
+    public LocalDate getBirthDay() {
         return birthDay;
     }
 
@@ -45,17 +45,7 @@ public void setGender(Gender gender) {
     }
 
     public int getAge() {
-        Calendar now = Calendar.getInstance();
-        Calendar birth = Calendar.getInstance();
-        birth.setTime(getBirthDay());
-
-        int years = now.get(Calendar.YEAR) - birth.get(Calendar.YEAR);
-        if(now.get(Calendar.MONTH) > birth.get(Calendar.MONTH) ||
-                now.get(Calendar.MONTH) == birth.get(Calendar.MONTH) && birth.get(Calendar.DATE) > now.get(Calendar.DATE)) {
-            years--;
-        }
-
-        return years;
+        return Period.between(getBirthDay(), LocalDate.now()).getYears();
     }
 
     @Override
@@ -68,14 +58,14 @@ public boolean equals(Object o) {
         if (birthDay != null ? !birthDay.equals(person.birthDay) : person.birthDay != null) return false;
         if (gender != person.gender) return false;
         if (lastName != null ? !lastName.equals(person.lastName) : person.lastName != null) return false;
-        if (name != null ? !name.equals(person.name) : person.name != null) return false;
+        if (firstName != null ? !firstName.equals(person.firstName) : person.firstName != null) return false;
 
         return true;
     }
 
     @Override
     public int hashCode() {
-        int result = name != null ? name.hashCode() : 0;
+        int result = firstName != null ? firstName.hashCode() : 0;
         result = 31 * result + (lastName != null ? lastName.hashCode() : 0);
         result = 31 * result + (birthDay != null ? birthDay.hashCode() : 0);
         result = 31 * result + (gender != null ? gender.hashCode() : 0);
@@ -85,7 +75,7 @@ public int hashCode() {
     @Override
     public String toString() {
         return "Person{" +
-                "name='" + name + '\'' +
+                "firstName='" + firstName + '\'' +
                 ", lastName='" + lastName + '\'' +
                 ", birthDay=" + birthDay +
                 ", gender=" + gender +
diff --git a/src/main/java/de/codecentric/java8examples/lambdas/SpringJdbcSupportWithLambdas.java b/src/main/java/de/codecentric/java8examples/lambdas/SpringJdbcSupportWithLambdas.java
index cebb772..ad1d284 100644
--- a/src/main/java/de/codecentric/java8examples/lambdas/SpringJdbcSupportWithLambdas.java
+++ b/src/main/java/de/codecentric/java8examples/lambdas/SpringJdbcSupportWithLambdas.java
@@ -19,7 +19,7 @@ public Person findPersonById(String id) {
                 new RowMapper<Person>() {
                     @Override
                     public Person mapRow(ResultSet rs, int i) throws SQLException {
-                        return new Person(rs.getString("FIRST_NAME"), rs.getString("LAST_NAME"), rs.getDate(3), Person.Gender.MALE);
+                        return new Person(rs.getString("FIRST_NAME"), rs.getString("LAST_NAME"), rs.getDate(3).toLocalDate(), Person.Gender.MALE);
                     }
                 });
     }
@@ -27,7 +27,7 @@ public Person mapRow(ResultSet rs, int i) throws SQLException {
     public Person findPersonByIdWithLambdas(String id) {
         return getJdbcTemplate().queryForObject(
                 "SELECT * FROM persons WHERE id = " + id,
-                (rs, i) -> new Person(rs.getString("FIRST_NAME"), rs.getString("LAST_NAME"), rs.getDate(3), Person.Gender.MALE));
+                (rs, i) -> new Person(rs.getString("FIRST_NAME"), rs.getString("LAST_NAME"), rs.getDate(3).toLocalDate(), Person.Gender.MALE));
     }
 
     // if things get messy, use a method reference
@@ -40,7 +40,7 @@ private Person mapPerson(ResultSet rs, int i) throws SQLException {
         return new Person(
                 rs.getString("FIRST_NAME"),
                 rs.getString("LAST_NAME"),
-                rs.getDate(3),
+                rs.getDate(3).toLocalDate(),
                 Person.Gender.MALE);
     }
 }
diff --git a/src/main/java/de/codecentric/java8examples/streaming/Collecting.java b/src/main/java/de/codecentric/java8examples/streaming/Collecting.java
new file mode 100644
index 0000000..a13661b
--- /dev/null
+++ b/src/main/java/de/codecentric/java8examples/streaming/Collecting.java
@@ -0,0 +1,38 @@
+package de.codecentric.java8examples.streaming;
+
+import de.codecentric.java8examples.Invoice;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Stream;
+
+/**
+ * Your task: Implement the following methods and make the tests passs.
+ */
+public class Collecting {
+
+    /**
+     * Identify the cheapest product (by pricePerUnit) in all invoices.
+     */
+    public static String cheapestProduct(List<Invoice> invoices) {
+        return "";
+    }
+
+    /**
+     * Identify the invoice with the highest total amount.
+     */
+    public static Invoice mostExpensiveInvoice(List<Invoice> invoices) {
+        return null;
+    }
+
+    /**
+     * For every product, compute the cheapest dealer. Return as a Map where the key is the product name and the value
+     * is the dealer (=sender of the invoice).
+     */
+    public static Map<String, String> cheapestDealersByProduct() {
+        return Collections.emptyMap();
+    }
+
+}
diff --git a/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java b/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
new file mode 100644
index 0000000..c751e9f
--- /dev/null
+++ b/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
@@ -0,0 +1,59 @@
+package de.codecentric.java8examples.streaming;
+
+import de.codecentric.java8examples.Invoice;
+import de.codecentric.java8examples.Person;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * Your task: Implement the following methods and make the tests passs.
+ */
+public class FilteringAndMapping {
+
+    /**
+     * Extract a list of names (firstname and lastname separated by space) from a given list of Person objects.
+     */
+    public static List<String> extractNames(List<Person> persons) {
+        return Collections.emptyList();
+    }
+
+    /**
+     * Extract a sorted (ascending by lastname) list of names (firstname and lastname separated by space) from a
+     * given list of Person objects.
+     */
+    public static List<String> extractNamesSortedByLastname(List<Person> persons) {
+        return Collections.emptyList();
+    }
+
+    /**
+     * From a given list of Person objects, extract a list of female firstnames
+     */
+    public static List<String> extractFemaleFirstnames(List<Person> persons) {
+        return Collections.emptyList();
+    }
+
+    /**
+     * Extract all females older than 18 years from a given list of Person objects.
+     */
+    public static List<Person> extractAdultWomen(List<Person> persons) {
+        return Collections.emptyList();
+    }
+
+    /**
+     * From a given list of Person objects, extract a set of firstnames of the people whose lastname starts
+     * with the given string.
+     */
+    public static Set<String> extractFirstnamesWhereLastnameStartsWith(List<Person> persons, String startsWith) {
+        return Collections.emptySet();
+    }
+
+    /**
+     * From a given list of invoices, extract a set of all product names.
+     */
+    public static Set<String> extractAllProducts(List<Invoice> invoices) {
+        return Collections.emptySet();
+    }
+}
+
diff --git a/src/test/java/de/codecentric/java8examples/TestData.java b/src/test/java/de/codecentric/java8examples/TestData.java
new file mode 100644
index 0000000..ce92165
--- /dev/null
+++ b/src/test/java/de/codecentric/java8examples/TestData.java
@@ -0,0 +1,36 @@
+package de.codecentric.java8examples;
+
+import java.math.BigDecimal;
+import java.time.LocalDate;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Utility class that generates some test data for us.
+ */
+public class TestData {
+    public static List<Person> listOfPersons() {
+        return Arrays.asList(
+                new Person("Jane", "Jungle", LocalDate.of(1978, 12, 15), Person.Gender.FEMALE),
+                new Person("Mary", "Smith", LocalDate.of(1980, 10, 19), Person.Gender.FEMALE),
+                new Person("John", "Dole", LocalDate.of(1973, 5, 31), Person.Gender.MALE),
+                new Person("Michael", "Abrahams", LocalDate.of(1967, 2, 1), Person.Gender.MALE),
+                new Person("Chris", "Cross", LocalDate.of(1985, 8, 22), Person.Gender.MALE),
+                new Person("Pete", "Power", LocalDate.of(1981, 3, 18), Person.Gender.MALE),
+                new Person("Maggie", "Simpson", LocalDate.of(2012, 10, 18), Person.Gender.FEMALE)
+        );
+    }
+
+    public static List<Invoice> listOfInvoices() {
+        return Arrays.asList(
+                new Invoice("Moe", "Homer", Arrays.asList(
+                        new InvoiceItem("Beer", 13, BigDecimal.valueOf(1.5)),
+                        new InvoiceItem("Burger", 3, BigDecimal.valueOf(4.5)))),
+                new Invoice("Crusty Burger", "Homer", Arrays.asList(
+                        new InvoiceItem("Burger", 5, BigDecimal.valueOf(5)),
+                        new InvoiceItem("Coke", 1, BigDecimal.valueOf(5)))),
+                new Invoice("Crusty Burger", "Bart", Arrays.asList(
+                        new InvoiceItem("Coke", 1, BigDecimal.valueOf(5)))));
+    }
+}
diff --git a/src/test/java/de/codecentric/java8examples/TestUtil.java b/src/test/java/de/codecentric/java8examples/TestUtil.java
deleted file mode 100644
index 36b71ee..0000000
--- a/src/test/java/de/codecentric/java8examples/TestUtil.java
+++ /dev/null
@@ -1,27 +0,0 @@
-package de.codecentric.java8examples;
-
-import java.time.LocalDate;
-import java.util.ArrayList;
-import java.util.Date;
-import java.util.List;
-
-/**
- * Utility class that generates some test data for us.
- */
-public class TestUtil {
-
-    public static Date dateOf(int month, int day, int year) {
-        return new Date(LocalDate.of(year, month, day).toEpochDay());
-    }
-
-    public static List<Person> getPersons() {
-        List<Person> list = new ArrayList<>();
-        list.add(new Person("Jane", "Jungle", dateOf(12, 15, 1978), Person.Gender.FEMALE));
-        list.add(new Person("Mary", "Smith", dateOf(10, 19, 1980), Person.Gender.FEMALE));
-        list.add(new Person("John", "Dole", dateOf(5, 31, 1973), Person.Gender.MALE));
-        list.add(new Person("Michael", "Abrahams", dateOf(2, 1, 1967), Person.Gender.MALE));
-        list.add(new Person("Chris", "Cross", dateOf(8, 22, 1985), Person.Gender.MALE));
-        list.add(new Person("Pete", "Power", dateOf(3, 18, 1981), Person.Gender.MALE));
-        return list;
-    }
-}
diff --git a/src/test/java/de/codecentric/java8examples/lambdas/LambdaBasedComparatorTest.java b/src/test/java/de/codecentric/java8examples/lambdas/LambdaBasedComparatorTest.java
index 1d1a737..e9e7f58 100644
--- a/src/test/java/de/codecentric/java8examples/lambdas/LambdaBasedComparatorTest.java
+++ b/src/test/java/de/codecentric/java8examples/lambdas/LambdaBasedComparatorTest.java
@@ -1,6 +1,6 @@
 package de.codecentric.java8examples.lambdas;
 
-import static de.codecentric.java8examples.TestUtil.getPersons;
+import static de.codecentric.java8examples.TestData.listOfPersons;
 import static org.hamcrest.number.OrderingComparison.lessThanOrEqualTo;
 import static org.junit.Assert.assertThat;
 
@@ -21,7 +21,7 @@ public class LambdaBasedComparatorTest {
 
     @Before
     public void setUp() throws Exception {
-        persons = getPersons();
+        persons = listOfPersons();
     }
 
     @Test
diff --git a/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java b/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java
index 676c108..abe63fd 100644
--- a/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java
+++ b/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java
@@ -1,9 +1,9 @@
 package de.codecentric.java8examples.lambdas;
 
-import static de.codecentric.java8examples.TestUtil.dateOf;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
+import java.time.LocalDate;
 import java.util.function.Predicate;
 
 import de.codecentric.java8examples.Person;
@@ -21,7 +21,7 @@ public class LambdaExampleTest {
     @Before
     public void setUp() throws Exception {
         // Nerd info: 5/15/1962 was the release date of Amazing Fantasy #15, where Spider Man had his first appearance
-        peter = new Person("Peter", "Parker", dateOf(8, 15, 1962), Person.Gender.MALE);
+        peter = new Person("Peter", "Parker", LocalDate.of(1962, 8, 15), Person.Gender.MALE);
         example = new LambdaExample<>(peter);
     }
 
diff --git a/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java b/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java
new file mode 100644
index 0000000..e060896
--- /dev/null
+++ b/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java
@@ -0,0 +1,68 @@
+package de.codecentric.java8examples.streaming;
+
+import de.codecentric.java8examples.Invoice;
+import de.codecentric.java8examples.Person;
+import de.codecentric.java8examples.TestData;
+import org.hamcrest.MatcherAssert;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.containsInAnyOrder;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Tests for mapping and filtering feature of the streaming api. Once you have completed the stub-methods in
+ * {@link FilteringAndMapping}, these tests should pass.
+ */
+public class FilteringAndMappingTest {
+
+    private List<Person> persons = TestData.listOfPersons();
+
+    private List<Invoice> invoices = TestData.listOfInvoices();
+
+    @Test
+    public void collectFirstNamesOfFemales() throws Exception {
+        // Matchers.contains should really be called "containsExactlyTheseElementsAndNoOtherElementsInExactlyThisOrder"
+        // I hate hamcrest :(
+        assertThat(FilteringAndMapping.extractFemaleFirstnames(persons), contains("Jane", "Mary", "Maggie"));
+    }
+
+    @Test
+    public void extractNames() {
+        assertThat(
+                FilteringAndMapping.extractNames(persons.subList(0, 6)),
+                contains("Jane Jungle", "Mary Smitch", "John Dole", "Michael Abrams", "Chris Cross", "Peter Power"));
+    }
+
+    @Test
+    public void extractNamesSortedByLastname() {
+        assertThat(
+                FilteringAndMapping.extractNamesSortedByLastname(persons.subList(0, 6)),
+                contains("Michael Abrams", "Chris Cross", "John Dole", "Jane Jungle", "Peter Power", "Mary Smitch"));
+    }
+
+    @Test
+    public void extractAdultWomen() {
+        // Yes, I know, this test is time-dependent and will break in a few months/years...
+        assertThat(
+                FilteringAndMapping.extractAdultWomen(persons),
+                contains(
+                        persons.get(0),
+                        persons.get(1)));
+    }
+
+    @Test
+    public void extractFirstnamesWhereLastnameStartsWith() {
+        assertThat(
+                FilteringAndMapping.extractFirstnamesWhereLastnameStartsWith(persons, "S"),
+                contains("Mary", "Maggie"));
+    }
+
+    @Test
+    public void testExtractAllProducts() throws Exception {
+        MatcherAssert.assertThat(FilteringAndMapping.extractAllProducts(invoices),
+                containsInAnyOrder("Beer", "Burrito", "Coke"));
+    }
+}
diff --git a/src/test/java/de/codecentric/java8examples/streaming/FlatMapTest.java b/src/test/java/de/codecentric/java8examples/streaming/FlatMapTest.java
new file mode 100644
index 0000000..a63f256
--- /dev/null
+++ b/src/test/java/de/codecentric/java8examples/streaming/FlatMapTest.java
@@ -0,0 +1,14 @@
+package de.codecentric.java8examples.streaming;
+
+
+import de.codecentric.java8examples.Invoice;
+import de.codecentric.java8examples.TestData;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.*;
+
+public class FlatMapTest {
+}
diff --git a/src/test/java/de/codecentric/java8examples/streaming/StreamingApiTest.java b/src/test/java/de/codecentric/java8examples/streaming/StreamingApiTest.java
deleted file mode 100644
index 142bdbb..0000000
--- a/src/test/java/de/codecentric/java8examples/streaming/StreamingApiTest.java
+++ /dev/null
@@ -1,58 +0,0 @@
-package de.codecentric.java8examples.streaming;
-
-import static de.codecentric.java8examples.TestUtil.getPersons;
-import static org.hamcrest.collection.IsIterableContainingInAnyOrder.containsInAnyOrder;
-import static org.junit.Assert.assertThat;
-
-import java.util.List;
-import java.util.function.Supplier;
-import java.util.stream.Collectors;
-import java.util.stream.Stream;
-
-import org.junit.Before;
-import org.junit.Test;
-
-import de.codecentric.java8examples.Person;
-
-/**
- * Test case showing the use of the streaming API.
- */
-public class StreamingApiTest {
-
-    private List<Person> persons;
-
-    @Before
-    public void setUp() throws Exception {
-        persons = getPersons();
-    }
-
-    @Test
-    public void collectLastNamesOfFemales() throws Exception {
-        List<String> femaleLastNames =
-                persons.stream()
-                .filter(p -> p.getGender().equals(Person.Gender.FEMALE))
-                .<String> map(p -> p.getLastName())
-                .collect(Collectors.<String> toList());
-
-        assertThat(femaleLastNames, containsInAnyOrder("Jungle", "Smith"));
-    }
-
-    @Test
-    public void testName() throws Exception {
-        Stream<Integer> stream = Stream.generate(new Supplier<Integer>() {
-            int count = 0;
-
-            @Override
-            public Integer get() {
-                System.out.println("get" + count);
-                return count++;
-            }
-        });
-
-        stream
-                .filter(i -> i.intValue() % 2 == 0)
-                .limit(100);
-
-
-    }
-}

From 05df5bbad9bdcc6b139e7dfba5f4cdca823df185 Mon Sep 17 00:00:00 2001
From: "daniel.reuter@codecentric.de" <reuter@daniels-mbp.codecentric.local>
Date: Thu, 28 Nov 2013 12:49:42 +0100
Subject: [PATCH 02/23] Maven und Time-Test

---
 pom.xml                                                |  3 ---
 .../codecentric/java8examples/timeapi/TimeApiTest.java | 10 +++++-----
 2 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/pom.xml b/pom.xml
index fd23cad..3d02b42 100644
--- a/pom.xml
+++ b/pom.xml
@@ -39,9 +39,6 @@
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-eclipse-plugin</artifactId>
 				<configuration>
-					<classpathContainers>
-						<classpathContainer>org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/jdk1.8.0</classpathContainer>
-					</classpathContainers>
 					<downloadSources>true</downloadSources>
 					<downloadJavadocs>true</downloadJavadocs>
 					<source>1.8</source>
diff --git a/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java b/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java
index 2a6e6e7..a86fec7 100644
--- a/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java
+++ b/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java
@@ -80,14 +80,14 @@ public void timeBetweenToDates() {
 	Period between = Period.between(birthday, LocalDate.now());
 	System.out.println(between.getYears() + " Years " + between.getMonths() + " Months " + between.getDays() + " Days.");
 	assertEquals(32, between.getYears());
-	assertEquals(1, between.getMonths());
+	assertEquals(2, between.getMonths());
 
 	// Joda
 	org.joda.time.LocalDate birthdayJoda = new org.joda.time.LocalDate(1981, 9, 3);
 	org.joda.time.Period betweenJoda = new org.joda.time.Period(birthdayJoda, org.joda.time.LocalDate.now());
 	System.out.println(betweenJoda.getYears() + " Years " + betweenJoda.getMonths() + " Months " + betweenJoda.getDays() + " Days.");
 	assertEquals(32, betweenJoda.getYears());
-	assertEquals(1, betweenJoda.getMonths());
+	assertEquals(2, betweenJoda.getMonths()); 
     }
 
     @Test
@@ -152,7 +152,7 @@ public void timezoneAndOffset() {
 	ZonedDateTime zonedDateTimeEurope = ZonedDateTime.now();
 	ZonedDateTime zonedDateTimeUTC = ZonedDateTime.now(ZoneId.of("UTC"));
 
-	assertEquals(60 * 60 * 2, zonedDateTimeEurope.getOffset().getTotalSeconds());
+	assertEquals(60 * 60 * 1, zonedDateTimeEurope.getOffset().getTotalSeconds());
 	assertEquals("Europe/Berlin", zonedDateTimeEurope.getZone().getId());
 	assertFalse(zonedDateTimeEurope.isBefore(zonedDateTimeUTC));
 	assertFalse(zonedDateTimeEurope.isAfter(zonedDateTimeUTC));
@@ -162,7 +162,7 @@ public void timezoneAndOffset() {
 	DateTime dateTimeEuropeJoda = DateTime.now();
 	DateTime dateTimeUTCJoda = DateTime.now(DateTimeZone.UTC);
 
-	assertEquals(60 * 60 * 2 * 1000, dateTimeEuropeJoda.getZone().getOffset(dateTimeEuropeJoda.getMillis()));
+	assertEquals(60 * 60 * 1 * 1000, dateTimeEuropeJoda.getZone().getOffset(dateTimeEuropeJoda.getMillis()));
 	assertEquals("Europe/Berlin", dateTimeEuropeJoda.getZone().getID());
 	assertFalse(dateTimeEuropeJoda.isBefore(dateTimeUTCJoda));
 	assertFalse(dateTimeEuropeJoda.isAfter(dateTimeUTCJoda));
@@ -170,7 +170,7 @@ public void timezoneAndOffset() {
     }
 
     // TODO Formatting & Parsing
-    // TODO Conversion Hibernate? SQL - zurück zu util.date
+    // TODO Conversion Hibernate? SQL - zur��ck zu util.date
     // TODO Null-Handling und beschriebene Unterschiede
 
 }
\ No newline at end of file

From c7486795652a152d99d2f2fd781d3b0265c7a07f Mon Sep 17 00:00:00 2001
From: Daniel Reuter <daniel.reuter@codecentric.de>
Date: Thu, 28 Nov 2013 19:23:13 +0100
Subject: [PATCH 03/23] JSR-310 Parsing-Formatting

---
 .../java8examples/timeapi/TimeApiTest.java    | 27 +++++++++++++------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java b/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java
index a86fec7..b21cfe2 100644
--- a/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java
+++ b/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java
@@ -10,6 +10,7 @@
 import java.time.ZoneId;
 import java.time.ZonedDateTime;
 import java.time.chrono.ThaiBuddhistDate;
+import java.time.format.DateTimeFormatter;
 import java.time.temporal.ChronoField;
 
 import org.joda.time.DateTime;
@@ -17,15 +18,14 @@
 import org.joda.time.DateTimeZone;
 import org.joda.time.Interval;
 import org.joda.time.chrono.BuddhistChronology;
+import org.joda.time.format.DateTimeFormat;
 import org.junit.Test;
 
 /**
  * <a href="http://blog.joda.org/2009/11/why-jsr-310-isn-joda-time_4941.html">Why JSR-310 isn't Joda-Time</a><br/>
  * <a href="http://jug.ua/wp-content/uploads/2013/02/JODAjsr310.pdf">nice presentation (JUG Ukraine)</a><br/>
  * <a href="http://openjdk.java.net/projects/threeten/">project page</a><br/>
- * <a href="http://greannetwork.wordpress.com/2012/12/11/jsr-310-date-and-time-api-example/">examples 1</a><br/>
- * <a href="https://today.java.net/pub/a/today/2008/09/18/jsr-310-new-java-date-time-api.html">examples 2</a><br/>
- * <a href="http://download.java.net/jdk8/docs/api/java/time/package-summary.html">Java-Doc/a><br/>
+ * <a href= "http://download.java.net/jdk8/docs/api/java/time/package-summary.html" >Java-Doc</a><br/>
  * 
  * <br>
  * <h3>Joda</h3>
@@ -87,7 +87,7 @@ public void timeBetweenToDates() {
 	org.joda.time.Period betweenJoda = new org.joda.time.Period(birthdayJoda, org.joda.time.LocalDate.now());
 	System.out.println(betweenJoda.getYears() + " Years " + betweenJoda.getMonths() + " Months " + betweenJoda.getDays() + " Days.");
 	assertEquals(32, betweenJoda.getYears());
-	assertEquals(2, betweenJoda.getMonths()); 
+	assertEquals(2, betweenJoda.getMonths());
     }
 
     @Test
@@ -154,7 +154,7 @@ public void timezoneAndOffset() {
 
 	assertEquals(60 * 60 * 1, zonedDateTimeEurope.getOffset().getTotalSeconds());
 	assertEquals("Europe/Berlin", zonedDateTimeEurope.getZone().getId());
-	assertFalse(zonedDateTimeEurope.isBefore(zonedDateTimeUTC));
+	assertFalse(zonedDateTimeEurope.isBefore(zonedDateTimeUTC)); 
 	assertFalse(zonedDateTimeEurope.isAfter(zonedDateTimeUTC));
 	assertTrue(zonedDateTimeEurope.isEqual(zonedDateTimeUTC));
 
@@ -169,8 +169,19 @@ public void timezoneAndOffset() {
 	assertTrue(dateTimeEuropeJoda.isEqual(dateTimeUTCJoda));
     }
 
-    // TODO Formatting & Parsing
-    // TODO Conversion Hibernate? SQL - zur��ck zu util.date
-    // TODO Null-Handling und beschriebene Unterschiede
+    @Test
+    public void parsingAndFormatting() {
+	// JSR-310
+	DateTimeFormatter fmt = DateTimeFormatter.ofPattern("dd.MM.yyyy");
+	LocalDate parsedDate = LocalDate.parse("03.09.1981", fmt);
+	assertEquals(LocalDate.of(1981, 9, 3), parsedDate);
+	assertEquals("03.09.1981", fmt.format(LocalDate.of(1981, 9, 3)));
+
+	// Joda
+	org.joda.time.format.DateTimeFormatter fmtJoda = DateTimeFormat.forPattern("dd.MM.yyyy");
+	org.joda.time.LocalDate parsedDateJoda = org.joda.time.LocalDate.parse("03.09.1981", fmtJoda);
+	assertEquals(new org.joda.time.LocalDate(1981, 9, 3), parsedDateJoda);
+	assertEquals("03.09.1981", fmtJoda.print(new org.joda.time.LocalDate(1981, 9, 3)));
+    }
 
 }
\ No newline at end of file

From f99f0afeae65c2e2ebd7f2560689b6601bf5b3a8 Mon Sep 17 00:00:00 2001
From: Daniel Reuter <daniel.reuter@codecentric.de>
Date: Fri, 29 Nov 2013 10:52:43 +0100
Subject: [PATCH 04/23] java.util.Date - examples

---
 .../java8examples/timeapi/TimeApiTest.java    | 93 ++++++++++++++++---
 1 file changed, 80 insertions(+), 13 deletions(-)

diff --git a/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java b/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java
index b21cfe2..419aee6 100644
--- a/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java
+++ b/src/test/java/de/codecentric/java8examples/timeapi/TimeApiTest.java
@@ -4,7 +4,11 @@
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
+import java.text.DateFormat;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
 import java.time.LocalDate;
+import java.time.LocalDateTime;
 import java.time.Month;
 import java.time.Period;
 import java.time.ZoneId;
@@ -12,6 +16,10 @@
 import java.time.chrono.ThaiBuddhistDate;
 import java.time.format.DateTimeFormatter;
 import java.time.temporal.ChronoField;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.GregorianCalendar;
+import java.util.TimeZone;
 
 import org.joda.time.DateTime;
 import org.joda.time.DateTimeFieldType;
@@ -21,6 +29,8 @@
 import org.joda.time.format.DateTimeFormat;
 import org.junit.Test;
 
+import sun.util.BuddhistCalendar;
+
 /**
  * <a href="http://blog.joda.org/2009/11/why-jsr-310-isn-joda-time_4941.html">Why JSR-310 isn't Joda-Time</a><br/>
  * <a href="http://jug.ua/wp-content/uploads/2013/02/JODAjsr310.pdf">nice presentation (JUG Ukraine)</a><br/>
@@ -88,6 +98,14 @@ public void timeBetweenToDates() {
 	System.out.println(betweenJoda.getYears() + " Years " + betweenJoda.getMonths() + " Months " + betweenJoda.getDays() + " Days.");
 	assertEquals(32, betweenJoda.getYears());
 	assertEquals(2, betweenJoda.getMonths());
+	
+	// Date & Calendar
+	Calendar birthdayCalendar = Calendar.getInstance();
+	birthdayCalendar.set(1981, Calendar.SEPTEMBER, 3);
+	int diffYears = Calendar.getInstance().get(Calendar.YEAR) - birthdayCalendar.get(Calendar.YEAR);
+	int diffMonth = Calendar.getInstance().get(Calendar.MONTH) - birthdayCalendar.get(Calendar.MONTH);
+	assertEquals(32, diffYears);
+	assertEquals(2, diffMonth);
     }
 
     @Test
@@ -102,11 +120,23 @@ public void checkDateIsInInterval() {
 	Interval interval = new Interval(new DateTime(1981, 9, 3, 12, 0), DateTime.now());
 	assertFalse(interval.contains(new DateTime(1980, 1, 1, 12, 0)));
 	assertTrue(interval.contains(new DateTime(1985, 1, 1, 12, 0)));
+	
+	// Date & Calendar
+	Calendar birthdayCalendar = Calendar.getInstance();
+	birthdayCalendar.set(1981, Calendar.SEPTEMBER, 3);
+	Calendar nowCalendar = Calendar.getInstance();
+	assertFalse(checkInterval(birthdayCalendar, nowCalendar, new GregorianCalendar(1980, 1, 1)));
+	assertTrue(checkInterval(birthdayCalendar, nowCalendar, new GregorianCalendar(1985, 1, 1)));
+	
     }
 
     private boolean checkInterval(LocalDate from, LocalDate to, LocalDate date) {
 	return from.isBefore(date) && to.isAfter(date);
     }
+    
+    private boolean checkInterval(Calendar from, Calendar to, Calendar date) {
+	return date.getTime().after(from.getTime()) && date.getTime().before(to.getTime());
+    }
 
     @Test
     public void calculate5Years() {
@@ -123,18 +153,24 @@ public void calculate5Years() {
 	assertEquals(birthdayPlusJoda.getDayOfMonth(), 3);
 	assertEquals(birthdayPlusJoda.getMonthOfYear(), 9);
 	assertEquals(birthdayPlusJoda.getYear(), 1991);
+	
+	// Date & Calendar
+	Calendar birthdayCalendar = Calendar.getInstance();
+	birthdayCalendar.set(1981, Calendar.SEPTEMBER, 3);
+	birthdayCalendar.add(Calendar.YEAR,10);
+	assertEquals(birthdayCalendar.get(Calendar.DAY_OF_MONTH), 3);
+	// !! 0-based
+	assertEquals(birthdayCalendar.get(Calendar.MONTH), Calendar.SEPTEMBER);
+	assertEquals(birthdayCalendar.get(Calendar.YEAR), 1991);
     }
 
     @Test
     public void chronologies() {
 	// JSR-310
 	ThaiBuddhistDate thaiBuddhistDate = ThaiBuddhistDate.now();
-	System.out.println(thaiBuddhistDate.getChronology());
 	int thaiYear = thaiBuddhistDate.get(ChronoField.YEAR);
 	LocalDate isoDate = LocalDate.now();
-	System.out.println(isoDate.getChronology());
 	int isoYear = isoDate.get(ChronoField.YEAR);
-
 	assertEquals(thaiYear, isoYear + 543);
 
 	// Joda
@@ -142,39 +178,59 @@ public void chronologies() {
 	int buddhistYearJoda = buddhistDateJoda.get(DateTimeFieldType.year());
 	org.joda.time.LocalDate dateJoda = new org.joda.time.LocalDate();
 	int yearJoda = dateJoda.get(DateTimeFieldType.year());
-
 	assertEquals(buddhistYearJoda, yearJoda + 543);
+	
+	// Date & Calendar
+	BuddhistCalendar buddhistCalendar = new BuddhistCalendar();
+	int buddhistYearCalendar = buddhistCalendar.get(BuddhistCalendar.YEAR);
+	Calendar calendar = Calendar.getInstance();
+	int yearCalendar = calendar.get(Calendar.YEAR);
+	assertEquals(buddhistYearCalendar, yearCalendar + 543);
     }
+    
 
     @Test
-    public void timezoneAndOffset() {
+    public void timezoneAndOffset() throws InterruptedException {
 	// JSR-310
-	ZonedDateTime zonedDateTimeEurope = ZonedDateTime.now();
-	ZonedDateTime zonedDateTimeUTC = ZonedDateTime.now(ZoneId.of("UTC"));
+	LocalDateTime dateTime = LocalDateTime.now();
+	ZonedDateTime zonedDateTimeEurope = ZonedDateTime.of(dateTime, ZoneId.systemDefault());
+	ZonedDateTime zonedDateTimeUTC = ZonedDateTime.of(dateTime, ZoneId.of("UTC"));
 
 	assertEquals(60 * 60 * 1, zonedDateTimeEurope.getOffset().getTotalSeconds());
 	assertEquals("Europe/Berlin", zonedDateTimeEurope.getZone().getId());
-	assertFalse(zonedDateTimeEurope.isBefore(zonedDateTimeUTC)); 
+	//!!
+	assertTrue(zonedDateTimeEurope.isBefore(zonedDateTimeUTC)); 
 	assertFalse(zonedDateTimeEurope.isAfter(zonedDateTimeUTC));
-	assertTrue(zonedDateTimeEurope.isEqual(zonedDateTimeUTC));
+	assertFalse(zonedDateTimeEurope.isEqual(zonedDateTimeUTC));
 
 	// Joda
-	DateTime dateTimeEuropeJoda = DateTime.now();
-	DateTime dateTimeUTCJoda = DateTime.now(DateTimeZone.UTC);
+	Date date = new Date();
+	DateTime dateTimeEuropeJoda = new DateTime(date.getTime(),DateTimeZone.getDefault());
+	DateTime dateTimeUTCJoda = new DateTime(date.getTime(),DateTimeZone.UTC);
 
 	assertEquals(60 * 60 * 1 * 1000, dateTimeEuropeJoda.getZone().getOffset(dateTimeEuropeJoda.getMillis()));
 	assertEquals("Europe/Berlin", dateTimeEuropeJoda.getZone().getID());
+	//!!
 	assertFalse(dateTimeEuropeJoda.isBefore(dateTimeUTCJoda));
 	assertFalse(dateTimeEuropeJoda.isAfter(dateTimeUTCJoda));
 	assertTrue(dateTimeEuropeJoda.isEqual(dateTimeUTCJoda));
+	
+	// Date & Calendar
+	Calendar calendarEurope = Calendar.getInstance();
+	calendarEurope.setTime(date);
+	Calendar calendarUTC = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
+	calendarEurope.setTime(date);
+	assertFalse(calendarEurope.getTime().before(calendarUTC.getTime()));
+	assertFalse(calendarEurope.getTime().after(calendarUTC.getTime()));
+	assertTrue(calendarEurope.getTime().equals(calendarUTC.getTime()));
     }
 
     @Test
     public void parsingAndFormatting() {
 	// JSR-310
 	DateTimeFormatter fmt = DateTimeFormatter.ofPattern("dd.MM.yyyy");
-	LocalDate parsedDate = LocalDate.parse("03.09.1981", fmt);
-	assertEquals(LocalDate.of(1981, 9, 3), parsedDate);
+	LocalDate parsedLocalDate = LocalDate.parse("03.09.1981", fmt);
+	assertEquals(LocalDate.of(1981, 9, 3), parsedLocalDate);
 	assertEquals("03.09.1981", fmt.format(LocalDate.of(1981, 9, 3)));
 
 	// Joda
@@ -182,6 +238,17 @@ public void parsingAndFormatting() {
 	org.joda.time.LocalDate parsedDateJoda = org.joda.time.LocalDate.parse("03.09.1981", fmtJoda);
 	assertEquals(new org.joda.time.LocalDate(1981, 9, 3), parsedDateJoda);
 	assertEquals("03.09.1981", fmtJoda.print(new org.joda.time.LocalDate(1981, 9, 3)));
+	
+	// Date & Calendar
+	DateFormat dateFormat = new SimpleDateFormat("dd.MM.yyyy");
+	Date parsedDate = null;
+	try {
+	    parsedDate= dateFormat.parse("03.09.1981");
+	} catch (ParseException e) {
+	    // handle
+	}
+	assertEquals(new GregorianCalendar(1981, Calendar.SEPTEMBER,3).getTime(), parsedDate);
+	assertEquals("03.09.1981", dateFormat.format(new GregorianCalendar(1981, Calendar.SEPTEMBER,3).getTime()));
     }
 
 }
\ No newline at end of file

From d301105ef0f2edec1b15b1c8f63d4aa829020c73 Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Fri, 29 Nov 2013 11:02:33 +0100
Subject: [PATCH 05/23] Tasks for collecting and reducing streams.

---
 .../java8examples/streaming/Collecting.java   |  38 ------
 .../streaming/CollectingAndReducing.java      | 125 ++++++++++++++++++
 .../codecentric/java8examples/TestData.java   |  18 ++-
 .../streaming/CollectingAndReducingTest.java  |  78 +++++++++++
 .../java8examples/streaming/FlatMapTest.java  |  14 --
 5 files changed, 220 insertions(+), 53 deletions(-)
 delete mode 100644 src/main/java/de/codecentric/java8examples/streaming/Collecting.java
 create mode 100644 src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
 create mode 100644 src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
 delete mode 100644 src/test/java/de/codecentric/java8examples/streaming/FlatMapTest.java

diff --git a/src/main/java/de/codecentric/java8examples/streaming/Collecting.java b/src/main/java/de/codecentric/java8examples/streaming/Collecting.java
deleted file mode 100644
index a13661b..0000000
--- a/src/main/java/de/codecentric/java8examples/streaming/Collecting.java
+++ /dev/null
@@ -1,38 +0,0 @@
-package de.codecentric.java8examples.streaming;
-
-import de.codecentric.java8examples.Invoice;
-
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-import java.util.stream.Stream;
-
-/**
- * Your task: Implement the following methods and make the tests passs.
- */
-public class Collecting {
-
-    /**
-     * Identify the cheapest product (by pricePerUnit) in all invoices.
-     */
-    public static String cheapestProduct(List<Invoice> invoices) {
-        return "";
-    }
-
-    /**
-     * Identify the invoice with the highest total amount.
-     */
-    public static Invoice mostExpensiveInvoice(List<Invoice> invoices) {
-        return null;
-    }
-
-    /**
-     * For every product, compute the cheapest dealer. Return as a Map where the key is the product name and the value
-     * is the dealer (=sender of the invoice).
-     */
-    public static Map<String, String> cheapestDealersByProduct() {
-        return Collections.emptyMap();
-    }
-
-}
diff --git a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
new file mode 100644
index 0000000..ce04d53
--- /dev/null
+++ b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
@@ -0,0 +1,125 @@
+package de.codecentric.java8examples.streaming;
+
+import de.codecentric.java8examples.Invoice;
+import de.codecentric.java8examples.Person;
+
+import java.math.BigDecimal;
+import java.util.*;
+import java.util.stream.Stream;
+
+/**
+ * Your task: Implement the following methods and make the tests passs.
+ */
+public class CollectingAndReducing {
+
+    /**
+     * Compute the average age of the given list of Persons.
+     */
+    public static Double averageAge(List<Person> persons) {
+        return Double.valueOf(0);
+    }
+
+    /**
+     * How old is the oldest person in the given list.
+     */
+    public static Integer maxAge(List<Person> persons) {
+        return Integer.valueOf(0);
+    }
+
+    /**
+     * Compute Age-Statistics (max, min, average, ...) for the given list of Persons.
+     */
+    public static DoubleSummaryStatistics ageStatistics(List<Person> persons) {
+        return null;
+    }
+
+    /**
+     * Build a comma-separated list of the firstnames of a list of Persons.
+     *
+     * Example-Result: "Maggie, Marge, Mary"
+     */
+    public static String buildCommaSeparatedListOfFirstNames(List<Person> persons) {
+        return "";
+    }
+
+    /**
+     * Identify the cheapest product (by pricePerUnit) in all invoices.
+     */
+    public static String cheapestProduct(List<Invoice> invoices) {
+        return "";
+    }
+
+    /**
+     * Identify the invoice with the highest total amount.
+     */
+    public static Invoice mostExpensiveInvoice(List<Invoice> invoices) {
+        return null;
+    }
+
+    /**
+     * Just what the method name says.
+     */
+    public static Map<String, List<Invoice>> groupInvoicesByReceiver(List<Invoice> invoices) {
+        return Collections.emptyMap();
+    }
+
+    /**
+     * Compute the total amount, that each receiver spent.
+     *
+     * Hint: Use the two-argument version of Collectors.groupingBy together with Collectors.mapping.
+     */
+    public static Map<String, BigDecimal> expensesByReceiver(List<Invoice> invoices) {
+        return Collections.emptyMap();
+    }
+
+    /**
+     * How many items of each product have been purchased?
+     */
+    public static Map<String, String> countByProduct(List<Invoice> invoices) {
+        return Collections.emptyMap();
+    }
+
+    /**
+     * For every product, compute the cheapest dealer. Return as a Map where the key is the product name and the value
+     * is the dealer (=sender of the invoice).
+     */
+    public static Map<String, String> cheapestDealersByProduct(List<Invoice> invoices) {
+        return Collections.emptyMap();
+    }
+
+    /**
+     * From a given list of invoices, compute for every dealer the available products together with its price.
+     */
+    public static Map<String, ProductWithPrice> computeDealerInventory(List<Invoice> invoices) {
+        return Collections.emptyMap();
+    }
+
+    /**
+     * For every buyer, compute a list of his favorite products (that is: a list of products ordered by the total count
+     * of items bought).
+     * For example: Homer bought 5 beers at Moes, 2 beers and a burger at Crustys. Then the result should look like this:
+     * {"Homer" -> ["Beer", "Burger"]}
+     */
+    public static Map<String, List<String>> favoriteArticlesByBuyer(List<Invoice> invoices) {
+        return Collections.EMPTY_MAP;
+    }
+
+    public static class ProductWithPrice {
+        private String productName;
+        private BigDecimal price;
+
+        public ProductWithPrice(String productName, BigDecimal price) {
+            this.productName = productName;
+            this.price = price;
+        }
+
+        public String getProductName() {
+            return productName;
+        }
+
+        public BigDecimal getPrice() {
+            return price;
+        }
+    }
+
+}
diff --git a/src/test/java/de/codecentric/java8examples/TestData.java b/src/test/java/de/codecentric/java8examples/TestData.java
index ce92165..26ffe1b 100644
--- a/src/test/java/de/codecentric/java8examples/TestData.java
+++ b/src/test/java/de/codecentric/java8examples/TestData.java
@@ -31,6 +31,22 @@ public static List<Invoice> listOfInvoices() {
                         new InvoiceItem("Burger", 5, BigDecimal.valueOf(5)),
                         new InvoiceItem("Coke", 1, BigDecimal.valueOf(5)))),
                 new Invoice("Crusty Burger", "Bart", Arrays.asList(
-                        new InvoiceItem("Coke", 1, BigDecimal.valueOf(5)))));
+                        new InvoiceItem("Coke", 1, BigDecimal.valueOf(5)))),
+                new Invoice("Kwik-E-Mart", "Homer", Arrays.asList(
+                        new InvoiceItem("Beer", 9, BigDecimal.valueOf(0.9)),
+                        new InvoiceItem("Chips", 2, BigDecimal.valueOf(0.5)))),
+                new Invoice("Moe", "Marge", Arrays.asList(
+                        new InvoiceItem("Beer", 1, BigDecimal.valueOf(1.5)))),
+                new Invoice("Kwik-E-Mart", "Bart", Arrays.asList(
+                        new InvoiceItem("Coke", 2, BigDecimal.valueOf(2.5)),
+                        new InvoiceItem("Chips", 2, BigDecimal.valueOf(0.5)))),
+                new Invoice("Kwik-E-Mart", "Marge", Arrays.asList(
+                        new InvoiceItem("Cake", 2, BigDecimal.valueOf(3.4)),
+                        new InvoiceItem("Corn Flakes", 5, BigDecimal.valueOf(2.3)))),
+                new Invoice("Moe", "Homer", Arrays.asList(
+                        new InvoiceItem("Beer", 5, BigDecimal.valueOf(1.5)))),
+                new Invoice("Flander's Left-Handed Store", "Marge", Arrays.asList(
+                        new InvoiceItem("Left-Handed Scissors", 1, BigDecimal.valueOf(10.0))))
+                );
     }
 }
diff --git a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
new file mode 100644
index 0000000..208eaa2
--- /dev/null
+++ b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
@@ -0,0 +1,78 @@
+package de.codecentric.java8examples.streaming;
+
+import de.codecentric.java8examples.Invoice;
+import de.codecentric.java8examples.Person;
+import de.codecentric.java8examples.TestData;
+import org.junit.Test;
+
+import java.util.List;
+
+/**
+ * Tests for mapping and filtering feature of the streaming api. Once you have completed the stub-methods in
+ * {@link FilteringAndMapping}, these tests should pass.
+ */
+public class CollectingAndReducingTest {
+    private List<Person> persons = TestData.listOfPersons();
+
+    private List<Invoice> invoices = TestData.listOfInvoices();
+
+    @Test
+    public void testAverageAge() throws Exception {
+
+    }
+
+    @Test
+    public void testMaxAge() throws Exception {
+
+    }
+
+    @Test
+    public void testAgeStatistics() throws Exception {
+
+    }
+
+    @Test
+    public void testBuildCommaSeparatedListOfFirstNames() throws Exception {
+
+    }
+
+    @Test
+    public void testCheapestProduct() throws Exception {
+
+    }
+
+    @Test
+    public void testMostExpensiveInvoice() throws Exception {
+
+    }
+
+    @Test
+    public void testGroupInvoicesByReceiver() throws Exception {
+
+    }
+
+    @Test
+    public void testExpensesByReceiver() throws Exception {
+
+    }
+
+    @Test
+    public void testCountByProduct() throws Exception {
+
+    }
+
+    @Test
+    public void testCheapestDealersByProduct() throws Exception {
+
+    }
+
+    @Test
+    public void testComputeDealerInventory() throws Exception {
+
+    }
+
+    @Test
+    public void testFavoriteArticlesByBuyer() throws Exception {
+
+    }
+}
diff --git a/src/test/java/de/codecentric/java8examples/streaming/FlatMapTest.java b/src/test/java/de/codecentric/java8examples/streaming/FlatMapTest.java
deleted file mode 100644
index a63f256..0000000
--- a/src/test/java/de/codecentric/java8examples/streaming/FlatMapTest.java
+++ /dev/null
@@ -1,14 +0,0 @@
-package de.codecentric.java8examples.streaming;
-
-
-import de.codecentric.java8examples.Invoice;
-import de.codecentric.java8examples.TestData;
-import org.junit.Test;
-
-import java.util.List;
-
-import static org.hamcrest.MatcherAssert.assertThat;
-import static org.hamcrest.Matchers.*;
-
-public class FlatMapTest {
-}

From 414add4efd8df7c22e040c9602664967587d2005 Mon Sep 17 00:00:00 2001
From: Benedikt Ritter <beneritter@gmail.com>
Date: Fri, 29 Nov 2013 11:07:20 +0100
Subject: [PATCH 06/23] Add example for anonymous implementation of callback

---
 .../MethodReferenceExampleTest.java                | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/test/java/de/codecentric/java8examples/methodreference/MethodReferenceExampleTest.java b/src/test/java/de/codecentric/java8examples/methodreference/MethodReferenceExampleTest.java
index 783d30b..ebff4c1 100644
--- a/src/test/java/de/codecentric/java8examples/methodreference/MethodReferenceExampleTest.java
+++ b/src/test/java/de/codecentric/java8examples/methodreference/MethodReferenceExampleTest.java
@@ -20,7 +20,19 @@ public void setUp() throws Exception {
     }
 
     @Test
-    public void methodReferencToFooMethod() throws Exception {
+    public void callbackWithoutMethodReference() throws Exception {
+        Callable<String> callable = new Callable<String>() {
+            @Override
+            public String call() throws Exception {
+                return myFoo.doSomething();
+            }
+        };
+
+        assertEquals(myFoo.doSomething(), callable.call());
+    }
+
+    @Test
+    public void callbackWithMethodReference() throws Exception {
         Callable<String> callable = myFoo::doSomething;
 
         assertEquals(myFoo.doSomething(), callable.call());

From 280ecaee497da0a3d10793c74b13cd0f01217d27 Mon Sep 17 00:00:00 2001
From: Benedikt Ritter <beneritter@gmail.com>
Date: Fri, 29 Nov 2013 11:17:59 +0100
Subject: [PATCH 07/23] Add example for different favors of implementing a
 lambda

---
 .../java8examples/lambdas/LambdaExampleTest.java | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java b/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java
index abe63fd..3feb748 100644
--- a/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java
+++ b/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java
@@ -34,10 +34,24 @@ public boolean test(Person person) {
                 return person.getAge() > 30;
             }
         }));
+    }
+
+    @Test
+    public void peterIsOlderThan30WithBlockLambda() throws Exception {
+        // new: implement the predicate using a block lambda expression
+        assertTrue(example.matches((Person p) -> {
+            return p.getAge() > 30;
+        }));
+    }
 
-        // new: implement the predicate using lambda expression
+    @Test
+    public void peterIsOlderThan30WithOneLineLambda() throws Exception {
+        // implement the predicate using a one line lambda expression
         assertTrue(example.matches((Person person) -> person.getAge() > 30));
+    }
 
+    @Test
+    public void peterIsOlderThan30WithTypeInference() throws Exception {
         // even shorter: let the compiler work out the correct type
         assertTrue(example.matches(p -> p.getAge() > 30));
     }

From d082c8efbb8070d8e5cbde3e88630d4f0a580560 Mon Sep 17 00:00:00 2001
From: Daniel Reuter <daniel.reuter@codecentric.de>
Date: Fri, 29 Nov 2013 13:23:12 +0100
Subject: [PATCH 08/23] Fixed test cases

---
 .../streaming/FilteringAndMappingTest.java    | 35 +++++++------------
 1 file changed, 13 insertions(+), 22 deletions(-)

diff --git a/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java b/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java
index e060896..ea28169 100644
--- a/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java
+++ b/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java
@@ -13,8 +13,8 @@
 import static org.junit.Assert.assertThat;
 
 /**
- * Tests for mapping and filtering feature of the streaming api. Once you have completed the stub-methods in
- * {@link FilteringAndMapping}, these tests should pass.
+ * Tests for mapping and filtering feature of the streaming api. Once you have completed the stub-methods in {@link FilteringAndMapping}, these tests should
+ * pass.
  */
 public class FilteringAndMappingTest {
 
@@ -24,45 +24,36 @@ public class FilteringAndMappingTest {
 
     @Test
     public void collectFirstNamesOfFemales() throws Exception {
-        // Matchers.contains should really be called "containsExactlyTheseElementsAndNoOtherElementsInExactlyThisOrder"
-        // I hate hamcrest :(
-        assertThat(FilteringAndMapping.extractFemaleFirstnames(persons), contains("Jane", "Mary", "Maggie"));
+	// Matchers.contains should really be called "containsExactlyTheseElementsAndNoOtherElementsInExactlyThisOrder"
+	// I hate hamcrest :(
+	assertThat(FilteringAndMapping.extractFemaleFirstnames(persons), contains("Jane", "Mary", "Maggie"));
     }
 
     @Test
     public void extractNames() {
-        assertThat(
-                FilteringAndMapping.extractNames(persons.subList(0, 6)),
-                contains("Jane Jungle", "Mary Smitch", "John Dole", "Michael Abrams", "Chris Cross", "Peter Power"));
+	assertThat(FilteringAndMapping.extractNames(persons.subList(0, 6)),
+		contains("Jane Jungle", "Mary Smith", "John Dole", "Michael Abrahams", "Chris Cross", "Pete Power"));
     }
 
     @Test
     public void extractNamesSortedByLastname() {
-        assertThat(
-                FilteringAndMapping.extractNamesSortedByLastname(persons.subList(0, 6)),
-                contains("Michael Abrams", "Chris Cross", "John Dole", "Jane Jungle", "Peter Power", "Mary Smitch"));
+	assertThat(FilteringAndMapping.extractNamesSortedByLastname(persons.subList(0, 6)),
+		contains("Michael Abrahams", "Chris Cross", "John Dole", "Jane Jungle", "Pete Power", "Mary Smith"));
     }
 
     @Test
     public void extractAdultWomen() {
-        // Yes, I know, this test is time-dependent and will break in a few months/years...
-        assertThat(
-                FilteringAndMapping.extractAdultWomen(persons),
-                contains(
-                        persons.get(0),
-                        persons.get(1)));
+	// Yes, I know, this test is time-dependent and will break in a few months/years...
+	assertThat(FilteringAndMapping.extractAdultWomen(persons), contains(persons.get(0), persons.get(1)));
     }
 
     @Test
     public void extractFirstnamesWhereLastnameStartsWith() {
-        assertThat(
-                FilteringAndMapping.extractFirstnamesWhereLastnameStartsWith(persons, "S"),
-                contains("Mary", "Maggie"));
+	assertThat(FilteringAndMapping.extractFirstnamesWhereLastnameStartsWith(persons, "S"), contains("Maggie", "Mary"));
     }
 
     @Test
     public void testExtractAllProducts() throws Exception {
-        MatcherAssert.assertThat(FilteringAndMapping.extractAllProducts(invoices),
-                containsInAnyOrder("Beer", "Burrito", "Coke"));
+	MatcherAssert.assertThat(FilteringAndMapping.extractAllProducts(invoices), containsInAnyOrder("Beer", "Burrito", "Coke"));
     }
 }

From e164a3b7b28965acf5ef5cba2f428b96266d08c4 Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Fri, 29 Nov 2013 13:51:35 +0100
Subject: [PATCH 09/23] Tests for CollectingAndReducing.

---
 .../de/codecentric/java8examples/Invoice.java | 43 ++++++++++++
 .../java8examples/InvoiceItem.java            | 31 +++++++++
 .../streaming/CollectingAndReducing.java      | 61 ++++++++++++-----
 .../streaming/FilteringAndMapping.java        |  1 +
 .../codecentric/java8examples/TestData.java   |  6 +-
 .../streaming/CollectingAndReducingTest.java  | 67 ++++++++++++++++---
 6 files changed, 180 insertions(+), 29 deletions(-)

diff --git a/src/main/java/de/codecentric/java8examples/Invoice.java b/src/main/java/de/codecentric/java8examples/Invoice.java
index 65e0418..bc82460 100644
--- a/src/main/java/de/codecentric/java8examples/Invoice.java
+++ b/src/main/java/de/codecentric/java8examples/Invoice.java
@@ -1,6 +1,8 @@
 package de.codecentric.java8examples;
 
+import java.math.BigDecimal;
 import java.util.List;
+import java.util.stream.Collectors;
 
 public class Invoice {
 
@@ -20,9 +22,50 @@ public List<InvoiceItem> getItems() {
         return items;
     }
 
+    public BigDecimal getTotal() {
+        return getItems().stream()
+                .map(invoice -> invoice
+                        .getPricePerUnit()
+                        .multiply(BigDecimal.valueOf(invoice.getQuantity())))
+                .collect(Collectors.reducing(
+                        BigDecimal.ZERO,
+                        (sum, elem) -> sum.add(elem)));
+    }
+
     public Invoice(String sender, String recipient, List<InvoiceItem> items) {
         this.sender = sender;
         this.recipient = recipient;
         this.items = items;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        Invoice invoice = (Invoice) o;
+
+        if (items != null ? !items.equals(invoice.items) : invoice.items != null) return false;
+        if (recipient != null ? !recipient.equals(invoice.recipient) : invoice.recipient != null) return false;
+        if (sender != null ? !sender.equals(invoice.sender) : invoice.sender != null) return false;
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = sender != null ? sender.hashCode() : 0;
+        result = 31 * result + (recipient != null ? recipient.hashCode() : 0);
+        result = 31 * result + (items != null ? items.hashCode() : 0);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "Invoice{" +
+                "sender='" + sender + '\'' +
+                ", recipient='" + recipient + '\'' +
+                ", items=" + items +
+                '}';
+    }
 }
diff --git a/src/main/java/de/codecentric/java8examples/InvoiceItem.java b/src/main/java/de/codecentric/java8examples/InvoiceItem.java
index 44ed6a4..3fb33bf 100644
--- a/src/main/java/de/codecentric/java8examples/InvoiceItem.java
+++ b/src/main/java/de/codecentric/java8examples/InvoiceItem.java
@@ -25,4 +25,35 @@ public InvoiceItem(String product, Integer quantity, BigDecimal pricePerUnit) {
         this.quantity = quantity;
         this.pricePerUnit = pricePerUnit;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        InvoiceItem that = (InvoiceItem) o;
+
+        if (pricePerUnit != null ? !pricePerUnit.equals(that.pricePerUnit) : that.pricePerUnit != null) return false;
+        if (product != null ? !product.equals(that.product) : that.product != null) return false;
+        if (quantity != null ? !quantity.equals(that.quantity) : that.quantity != null) return false;
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = product != null ? product.hashCode() : 0;
+        result = 31 * result + (quantity != null ? quantity.hashCode() : 0);
+        result = 31 * result + (pricePerUnit != null ? pricePerUnit.hashCode() : 0);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "InvoiceItem{" +
+                "product='" + product + '\'' +
+                ", quantity=" + quantity +
+                ", pricePerUnit=" + pricePerUnit +
+                '}';
+    }
 }
diff --git a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
index ce04d53..9e74c6e 100644
--- a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
+++ b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
@@ -1,11 +1,12 @@
 package de.codecentric.java8examples.streaming;
 
 import de.codecentric.java8examples.Invoice;
+import de.codecentric.java8examples.InvoiceItem;
 import de.codecentric.java8examples.Person;
 
 import java.math.BigDecimal;
 import java.util.*;
-import java.util.stream.Stream;
+import java.util.stream.Collectors;
 
 /**
  * Your task: Implement the following methods and make the tests passs.
@@ -16,67 +17,93 @@ public class CollectingAndReducing {
      * Compute the average age of the given list of Persons.
      */
     public static Double averageAge(List<Person> persons) {
-        return Double.valueOf(0);
+        return persons.stream()
+                .mapToInt(Person::getAge)
+                .average().getAsDouble();
+
     }
 
     /**
      * How old is the oldest person in the given list.
      */
     public static Integer maxAge(List<Person> persons) {
-        return Integer.valueOf(0);
+        return persons.stream()
+                .mapToInt(Person::getAge)
+                .max().getAsInt();
     }
 
     /**
      * Compute Age-Statistics (max, min, average, ...) for the given list of Persons.
      */
-    public static DoubleSummaryStatistics ageStatistics(List<Person> persons) {
-        return null;
+    public static IntSummaryStatistics ageStatistics(List<Person> persons) {
+        return persons.stream()
+                .mapToInt(Person::getAge)
+                .summaryStatistics();
     }
 
     /**
      * Build a comma-separated list of the firstnames of a list of Persons.
-     *
+     * <p/>
      * Example-Result: "Maggie, Marge, Mary"
      */
     public static String buildCommaSeparatedListOfFirstNames(List<Person> persons) {
-        return "";
+        return persons.stream()
+                .map(Person::getFirstName)
+                .collect(Collectors.joining(", "));
     }
 
     /**
      * Identify the cheapest product (by pricePerUnit) in all invoices.
      */
     public static String cheapestProduct(List<Invoice> invoices) {
-        return "";
+        return invoices.stream()
+                .flatMap(invoice -> invoice.getItems().stream())
+                .min(Comparator.comparing(InvoiceItem::getPricePerUnit))
+                .get().getProduct();
     }
 
     /**
      * Identify the invoice with the highest total amount.
      */
     public static Invoice mostExpensiveInvoice(List<Invoice> invoices) {
-        return null;
+        return invoices.stream()
+                .collect(Collectors.<Invoice>maxBy(
+                        Comparator.comparing(Invoice::getTotal))).get();
     }
 
     /**
      * Just what the method name says.
      */
-    public static Map<String, List<Invoice>> groupInvoicesByReceiver(List<Invoice> invoices) {
-        return Collections.emptyMap();
+    public static Map<String, List<Invoice>> groupInvoicesByRecipient(List<Invoice> invoices) {
+        return invoices.stream()
+                .collect(Collectors.groupingBy(Invoice::getRecipient));
     }
 
     /**
      * Compute the total amount, that each receiver spent.
-     *
+     * <p/>
      * Hint: Use the two-argument version of Collectors.groupingBy together with Collectors.mapping.
      */
-    public static Map<String, BigDecimal> expensesByReceiver(List<Invoice> invoices) {
-        return Collections.emptyMap();
+    public static Map<String, BigDecimal> expensesByRecipient(List<Invoice> invoices) {
+        return invoices.stream()
+                .collect(Collectors.groupingBy(
+                        Invoice::getRecipient,
+                        Collectors.mapping(
+                                Invoice::getTotal,
+                                Collectors.reducing(
+                                        BigDecimal.ZERO,
+                                        (sum, elem) -> sum.add(elem)))));
     }
 
     /**
      * How many items of each product have been purchased?
      */
-    public static Map<String, String> countByProduct(List<Invoice> invoices) {
-        return Collections.emptyMap();
+    public static Map<String, Integer> countByProduct(List<Invoice> invoices) {
+        return invoices.stream()
+                .flatMap(invoice -> invoice.getItems().stream())
+                .collect(Collectors.groupingBy(
+                        InvoiceItem::getProduct,
+                        Collectors.summingInt(InvoiceItem::getQuantity)));
     }
 
     /**
@@ -101,7 +128,7 @@ public static Map<String, ProductWithPrice> computeDealerInventory(List<Invoice>
      * {"Homer" -> ["Beer", "Burger"]}
      */
     public static Map<String, List<String>> favoriteArticlesByBuyer(List<Invoice> invoices) {
-        return Collections.EMPTY_MAP;
+        return Collections.emptyMap();
     }
 
     public static class ProductWithPrice {
diff --git a/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java b/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
index c751e9f..25c8574 100644
--- a/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
+++ b/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
@@ -1,6 +1,7 @@
 package de.codecentric.java8examples.streaming;
 
 import de.codecentric.java8examples.Invoice;
+import de.codecentric.java8examples.InvoiceItem;
 import de.codecentric.java8examples.Person;
 
 import java.util.Collections;
diff --git a/src/test/java/de/codecentric/java8examples/TestData.java b/src/test/java/de/codecentric/java8examples/TestData.java
index 26ffe1b..e694e76 100644
--- a/src/test/java/de/codecentric/java8examples/TestData.java
+++ b/src/test/java/de/codecentric/java8examples/TestData.java
@@ -24,14 +24,14 @@ public static List<Person> listOfPersons() {
 
     public static List<Invoice> listOfInvoices() {
         return Arrays.asList(
-                new Invoice("Moe", "Homer", Arrays.asList(
-                        new InvoiceItem("Beer", 13, BigDecimal.valueOf(1.5)),
-                        new InvoiceItem("Burger", 3, BigDecimal.valueOf(4.5)))),
                 new Invoice("Crusty Burger", "Homer", Arrays.asList(
                         new InvoiceItem("Burger", 5, BigDecimal.valueOf(5)),
                         new InvoiceItem("Coke", 1, BigDecimal.valueOf(5)))),
                 new Invoice("Crusty Burger", "Bart", Arrays.asList(
                         new InvoiceItem("Coke", 1, BigDecimal.valueOf(5)))),
+                new Invoice("Moe", "Homer", Arrays.asList(
+                        new InvoiceItem("Beer", 13, BigDecimal.valueOf(1.5)),
+                        new InvoiceItem("Burger", 3, BigDecimal.valueOf(4.5)))),
                 new Invoice("Kwik-E-Mart", "Homer", Arrays.asList(
                         new InvoiceItem("Beer", 9, BigDecimal.valueOf(0.9)),
                         new InvoiceItem("Chips", 2, BigDecimal.valueOf(0.5)))),
diff --git a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
index 208eaa2..d87330a 100644
--- a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
+++ b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
@@ -5,7 +5,14 @@
 import de.codecentric.java8examples.TestData;
 import org.junit.Test;
 
+import java.math.BigDecimal;
+import java.util.Arrays;
+import java.util.IntSummaryStatistics;
 import java.util.List;
+import java.util.Map;
+
+import static org.hamcrest.Matchers.*;
+import static org.hamcrest.MatcherAssert.assertThat;
 
 /**
  * Tests for mapping and filtering feature of the streaming api. Once you have completed the stub-methods in
@@ -15,45 +22,87 @@ public class CollectingAndReducingTest {
     private List<Person> persons = TestData.listOfPersons();
 
     private List<Invoice> invoices = TestData.listOfInvoices();
+    private List<String> recipients = Arrays.asList("Homer", "Bart", "Marge");
 
     @Test
     public void testAverageAge() throws Exception {
-
+        assertThat(
+                CollectingAndReducing.averageAge(persons),
+                closeTo(30.57D, 0.01));
     }
 
     @Test
     public void testMaxAge() throws Exception {
-
+        assertThat(
+                CollectingAndReducing.maxAge(persons),
+                equalTo(46));
     }
 
     @Test
     public void testAgeStatistics() throws Exception {
-
+        IntSummaryStatistics statistic = CollectingAndReducing.ageStatistics(persons);
+        assertThat(statistic.getAverage(), equalTo(30.571428571428573));
+        assertThat(statistic.getCount(), equalTo(7l));
+        assertThat(statistic.getMax(), equalTo(46));
+        assertThat(statistic.getMin(), equalTo(1));
+        assertThat(statistic.getSum(), equalTo(214l));
     }
 
     @Test
     public void testBuildCommaSeparatedListOfFirstNames() throws Exception {
-
+        assertThat(
+                CollectingAndReducing.buildCommaSeparatedListOfFirstNames(persons),
+                equalTo("Jane, Mary, John, Michael, Chris, Pete, Maggie"));
     }
 
     @Test
     public void testCheapestProduct() throws Exception {
-
+        assertThat(
+                CollectingAndReducing.cheapestProduct(invoices),
+                equalTo("Chips"));
     }
 
     @Test
     public void testMostExpensiveInvoice() throws Exception {
+        assertThat(
+                CollectingAndReducing.mostExpensiveInvoice(invoices),
+                equalTo(invoices.get(2)));
 
     }
 
     @Test
-    public void testGroupInvoicesByReceiver() throws Exception {
-
+    public void testGroupInvoicesByRecipient() throws Exception {
+        Map<String,List<Invoice>> invoicesByRecipient =
+                CollectingAndReducing.groupInvoicesByRecipient(invoices);
+        assertThat(invoicesByRecipient.keySet(), hasSize(recipients.size()));
+
+        for (String recipient: recipients) {
+            for (Invoice invoice: invoices) {
+                if (recipient.equals(invoice.getRecipient())) {
+                    assertThat(invoicesByRecipient.get(recipient),
+                            hasItem(invoice));
+                } else {
+                    assertThat(invoicesByRecipient.get(recipient),
+                        not(hasItem(invoice)));
+                }
+            }
+        }
     }
 
     @Test
-    public void testExpensesByReceiver() throws Exception {
-
+    public void testExpensesByRecipient() throws Exception {
+        Map<String,BigDecimal> expencesByRecipient =
+                CollectingAndReducing.expensesByRecipient(invoices);
+        assertThat(expencesByRecipient.keySet(), hasSize(invoices.size()));
+        for (String recipient: recipients) {
+            BigDecimal expenses = BigDecimal.ZERO;
+            for (Invoice invoice: invoices) {
+                if (recipient.equals(invoice.getRecipient())) {
+                    expenses = expenses.add(invoice.getTotal());
+                }
+            }
+            assertThat(expencesByRecipient.get(recipient), equalTo(expenses));
+        }
     }
 
     @Test

From a30316f5d4fd18f54b90a5a9baf33ce32957a857 Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Fri, 29 Nov 2013 13:51:35 +0100
Subject: [PATCH 10/23] Tests for CollectingAndReducing.

---
 .../de/codecentric/java8examples/Invoice.java | 43 ++++++++++++
 .../java8examples/InvoiceItem.java            | 31 +++++++++
 .../streaming/CollectingAndReducing.java      | 61 ++++++++++++-----
 .../streaming/FilteringAndMapping.java        |  1 +
 .../codecentric/java8examples/TestData.java   |  6 +-
 .../streaming/CollectingAndReducingTest.java  | 67 ++++++++++++++++---
 6 files changed, 180 insertions(+), 29 deletions(-)

diff --git a/src/main/java/de/codecentric/java8examples/Invoice.java b/src/main/java/de/codecentric/java8examples/Invoice.java
index 65e0418..bc82460 100644
--- a/src/main/java/de/codecentric/java8examples/Invoice.java
+++ b/src/main/java/de/codecentric/java8examples/Invoice.java
@@ -1,6 +1,8 @@
 package de.codecentric.java8examples;
 
+import java.math.BigDecimal;
 import java.util.List;
+import java.util.stream.Collectors;
 
 public class Invoice {
 
@@ -20,9 +22,50 @@ public List<InvoiceItem> getItems() {
         return items;
     }
 
+    public BigDecimal getTotal() {
+        return getItems().stream()
+                .map(invoice -> invoice
+                        .getPricePerUnit()
+                        .multiply(BigDecimal.valueOf(invoice.getQuantity())))
+                .collect(Collectors.reducing(
+                        BigDecimal.ZERO,
+                        (sum, elem) -> sum.add(elem)));
+    }
+
     public Invoice(String sender, String recipient, List<InvoiceItem> items) {
         this.sender = sender;
         this.recipient = recipient;
         this.items = items;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        Invoice invoice = (Invoice) o;
+
+        if (items != null ? !items.equals(invoice.items) : invoice.items != null) return false;
+        if (recipient != null ? !recipient.equals(invoice.recipient) : invoice.recipient != null) return false;
+        if (sender != null ? !sender.equals(invoice.sender) : invoice.sender != null) return false;
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = sender != null ? sender.hashCode() : 0;
+        result = 31 * result + (recipient != null ? recipient.hashCode() : 0);
+        result = 31 * result + (items != null ? items.hashCode() : 0);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "Invoice{" +
+                "sender='" + sender + '\'' +
+                ", recipient='" + recipient + '\'' +
+                ", items=" + items +
+                '}';
+    }
 }
diff --git a/src/main/java/de/codecentric/java8examples/InvoiceItem.java b/src/main/java/de/codecentric/java8examples/InvoiceItem.java
index 44ed6a4..3fb33bf 100644
--- a/src/main/java/de/codecentric/java8examples/InvoiceItem.java
+++ b/src/main/java/de/codecentric/java8examples/InvoiceItem.java
@@ -25,4 +25,35 @@ public InvoiceItem(String product, Integer quantity, BigDecimal pricePerUnit) {
         this.quantity = quantity;
         this.pricePerUnit = pricePerUnit;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        InvoiceItem that = (InvoiceItem) o;
+
+        if (pricePerUnit != null ? !pricePerUnit.equals(that.pricePerUnit) : that.pricePerUnit != null) return false;
+        if (product != null ? !product.equals(that.product) : that.product != null) return false;
+        if (quantity != null ? !quantity.equals(that.quantity) : that.quantity != null) return false;
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = product != null ? product.hashCode() : 0;
+        result = 31 * result + (quantity != null ? quantity.hashCode() : 0);
+        result = 31 * result + (pricePerUnit != null ? pricePerUnit.hashCode() : 0);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "InvoiceItem{" +
+                "product='" + product + '\'' +
+                ", quantity=" + quantity +
+                ", pricePerUnit=" + pricePerUnit +
+                '}';
+    }
 }
diff --git a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
index ce04d53..9e74c6e 100644
--- a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
+++ b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
@@ -1,11 +1,12 @@
 package de.codecentric.java8examples.streaming;
 
 import de.codecentric.java8examples.Invoice;
+import de.codecentric.java8examples.InvoiceItem;
 import de.codecentric.java8examples.Person;
 
 import java.math.BigDecimal;
 import java.util.*;
-import java.util.stream.Stream;
+import java.util.stream.Collectors;
 
 /**
  * Your task: Implement the following methods and make the tests passs.
@@ -16,67 +17,93 @@ public class CollectingAndReducing {
      * Compute the average age of the given list of Persons.
      */
     public static Double averageAge(List<Person> persons) {
-        return Double.valueOf(0);
+        return persons.stream()
+                .mapToInt(Person::getAge)
+                .average().getAsDouble();
+
     }
 
     /**
      * How old is the oldest person in the given list.
      */
     public static Integer maxAge(List<Person> persons) {
-        return Integer.valueOf(0);
+        return persons.stream()
+                .mapToInt(Person::getAge)
+                .max().getAsInt();
     }
 
     /**
      * Compute Age-Statistics (max, min, average, ...) for the given list of Persons.
      */
-    public static DoubleSummaryStatistics ageStatistics(List<Person> persons) {
-        return null;
+    public static IntSummaryStatistics ageStatistics(List<Person> persons) {
+        return persons.stream()
+                .mapToInt(Person::getAge)
+                .summaryStatistics();
     }
 
     /**
      * Build a comma-separated list of the firstnames of a list of Persons.
-     *
+     * <p/>
      * Example-Result: "Maggie, Marge, Mary"
      */
     public static String buildCommaSeparatedListOfFirstNames(List<Person> persons) {
-        return "";
+        return persons.stream()
+                .map(Person::getFirstName)
+                .collect(Collectors.joining(", "));
     }
 
     /**
      * Identify the cheapest product (by pricePerUnit) in all invoices.
      */
     public static String cheapestProduct(List<Invoice> invoices) {
-        return "";
+        return invoices.stream()
+                .flatMap(invoice -> invoice.getItems().stream())
+                .min(Comparator.comparing(InvoiceItem::getPricePerUnit))
+                .get().getProduct();
     }
 
     /**
      * Identify the invoice with the highest total amount.
      */
     public static Invoice mostExpensiveInvoice(List<Invoice> invoices) {
-        return null;
+        return invoices.stream()
+                .collect(Collectors.<Invoice>maxBy(
+                        Comparator.comparing(Invoice::getTotal))).get();
     }
 
     /**
      * Just what the method name says.
      */
-    public static Map<String, List<Invoice>> groupInvoicesByReceiver(List<Invoice> invoices) {
-        return Collections.emptyMap();
+    public static Map<String, List<Invoice>> groupInvoicesByRecipient(List<Invoice> invoices) {
+        return invoices.stream()
+                .collect(Collectors.groupingBy(Invoice::getRecipient));
     }
 
     /**
      * Compute the total amount, that each receiver spent.
-     *
+     * <p/>
      * Hint: Use the two-argument version of Collectors.groupingBy together with Collectors.mapping.
      */
-    public static Map<String, BigDecimal> expensesByReceiver(List<Invoice> invoices) {
-        return Collections.emptyMap();
+    public static Map<String, BigDecimal> expensesByRecipient(List<Invoice> invoices) {
+        return invoices.stream()
+                .collect(Collectors.groupingBy(
+                        Invoice::getRecipient,
+                        Collectors.mapping(
+                                Invoice::getTotal,
+                                Collectors.reducing(
+                                        BigDecimal.ZERO,
+                                        (sum, elem) -> sum.add(elem)))));
     }
 
     /**
      * How many items of each product have been purchased?
      */
-    public static Map<String, String> countByProduct(List<Invoice> invoices) {
-        return Collections.emptyMap();
+    public static Map<String, Integer> countByProduct(List<Invoice> invoices) {
+        return invoices.stream()
+                .flatMap(invoice -> invoice.getItems().stream())
+                .collect(Collectors.groupingBy(
+                        InvoiceItem::getProduct,
+                        Collectors.summingInt(InvoiceItem::getQuantity)));
     }
 
     /**
@@ -101,7 +128,7 @@ public static Map<String, ProductWithPrice> computeDealerInventory(List<Invoice>
      * {"Homer" -> ["Beer", "Burger"]}
      */
     public static Map<String, List<String>> favoriteArticlesByBuyer(List<Invoice> invoices) {
-        return Collections.EMPTY_MAP;
+        return Collections.emptyMap();
     }
 
     public static class ProductWithPrice {
diff --git a/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java b/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
index c751e9f..25c8574 100644
--- a/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
+++ b/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
@@ -1,6 +1,7 @@
 package de.codecentric.java8examples.streaming;
 
 import de.codecentric.java8examples.Invoice;
+import de.codecentric.java8examples.InvoiceItem;
 import de.codecentric.java8examples.Person;
 
 import java.util.Collections;
diff --git a/src/test/java/de/codecentric/java8examples/TestData.java b/src/test/java/de/codecentric/java8examples/TestData.java
index 26ffe1b..e694e76 100644
--- a/src/test/java/de/codecentric/java8examples/TestData.java
+++ b/src/test/java/de/codecentric/java8examples/TestData.java
@@ -24,14 +24,14 @@ public static List<Person> listOfPersons() {
 
     public static List<Invoice> listOfInvoices() {
         return Arrays.asList(
-                new Invoice("Moe", "Homer", Arrays.asList(
-                        new InvoiceItem("Beer", 13, BigDecimal.valueOf(1.5)),
-                        new InvoiceItem("Burger", 3, BigDecimal.valueOf(4.5)))),
                 new Invoice("Crusty Burger", "Homer", Arrays.asList(
                         new InvoiceItem("Burger", 5, BigDecimal.valueOf(5)),
                         new InvoiceItem("Coke", 1, BigDecimal.valueOf(5)))),
                 new Invoice("Crusty Burger", "Bart", Arrays.asList(
                         new InvoiceItem("Coke", 1, BigDecimal.valueOf(5)))),
+                new Invoice("Moe", "Homer", Arrays.asList(
+                        new InvoiceItem("Beer", 13, BigDecimal.valueOf(1.5)),
+                        new InvoiceItem("Burger", 3, BigDecimal.valueOf(4.5)))),
                 new Invoice("Kwik-E-Mart", "Homer", Arrays.asList(
                         new InvoiceItem("Beer", 9, BigDecimal.valueOf(0.9)),
                         new InvoiceItem("Chips", 2, BigDecimal.valueOf(0.5)))),
diff --git a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
index 208eaa2..d87330a 100644
--- a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
+++ b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
@@ -5,7 +5,14 @@
 import de.codecentric.java8examples.TestData;
 import org.junit.Test;
 
+import java.math.BigDecimal;
+import java.util.Arrays;
+import java.util.IntSummaryStatistics;
 import java.util.List;
+import java.util.Map;
+
+import static org.hamcrest.Matchers.*;
+import static org.hamcrest.MatcherAssert.assertThat;
 
 /**
  * Tests for mapping and filtering feature of the streaming api. Once you have completed the stub-methods in
@@ -15,45 +22,87 @@ public class CollectingAndReducingTest {
     private List<Person> persons = TestData.listOfPersons();
 
     private List<Invoice> invoices = TestData.listOfInvoices();
+    private List<String> recipients = Arrays.asList("Homer", "Bart", "Marge");
 
     @Test
     public void testAverageAge() throws Exception {
-
+        assertThat(
+                CollectingAndReducing.averageAge(persons),
+                closeTo(30.57D, 0.01));
     }
 
     @Test
     public void testMaxAge() throws Exception {
-
+        assertThat(
+                CollectingAndReducing.maxAge(persons),
+                equalTo(46));
     }
 
     @Test
     public void testAgeStatistics() throws Exception {
-
+        IntSummaryStatistics statistic = CollectingAndReducing.ageStatistics(persons);
+        assertThat(statistic.getAverage(), equalTo(30.571428571428573));
+        assertThat(statistic.getCount(), equalTo(7l));
+        assertThat(statistic.getMax(), equalTo(46));
+        assertThat(statistic.getMin(), equalTo(1));
+        assertThat(statistic.getSum(), equalTo(214l));
     }
 
     @Test
     public void testBuildCommaSeparatedListOfFirstNames() throws Exception {
-
+        assertThat(
+                CollectingAndReducing.buildCommaSeparatedListOfFirstNames(persons),
+                equalTo("Jane, Mary, John, Michael, Chris, Pete, Maggie"));
     }
 
     @Test
     public void testCheapestProduct() throws Exception {
-
+        assertThat(
+                CollectingAndReducing.cheapestProduct(invoices),
+                equalTo("Chips"));
     }
 
     @Test
     public void testMostExpensiveInvoice() throws Exception {
+        assertThat(
+                CollectingAndReducing.mostExpensiveInvoice(invoices),
+                equalTo(invoices.get(2)));
 
     }
 
     @Test
-    public void testGroupInvoicesByReceiver() throws Exception {
-
+    public void testGroupInvoicesByRecipient() throws Exception {
+        Map<String,List<Invoice>> invoicesByRecipient =
+                CollectingAndReducing.groupInvoicesByRecipient(invoices);
+        assertThat(invoicesByRecipient.keySet(), hasSize(recipients.size()));
+
+        for (String recipient: recipients) {
+            for (Invoice invoice: invoices) {
+                if (recipient.equals(invoice.getRecipient())) {
+                    assertThat(invoicesByRecipient.get(recipient),
+                            hasItem(invoice));
+                } else {
+                    assertThat(invoicesByRecipient.get(recipient),
+                        not(hasItem(invoice)));
+                }
+            }
+        }
     }
 
     @Test
-    public void testExpensesByReceiver() throws Exception {
-
+    public void testExpensesByRecipient() throws Exception {
+        Map<String,BigDecimal> expencesByRecipient =
+                CollectingAndReducing.expensesByRecipient(invoices);
+        assertThat(expencesByRecipient.keySet(), hasSize(invoices.size()));
+        for (String recipient: recipients) {
+            BigDecimal expenses = BigDecimal.ZERO;
+            for (Invoice invoice: invoices) {
+                if (recipient.equals(invoice.getRecipient())) {
+                    expenses = expenses.add(invoice.getTotal());
+                }
+            }
+            assertThat(expencesByRecipient.get(recipient), equalTo(expenses));
+        }
     }
 
     @Test

From af7a65db028193e709a4930640d3383d0d83de91 Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Fri, 29 Nov 2013 13:57:43 +0100
Subject: [PATCH 11/23] Remove solutions ;-)

---
 .../streaming/CollectingAndReducing.java      | 44 ++++---------------
 .../streaming/CollectingAndReducingTest.java  |  2 +
 2 files changed, 11 insertions(+), 35 deletions(-)

diff --git a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
index 9e74c6e..ae6be2b 100644
--- a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
+++ b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
@@ -17,28 +17,21 @@ public class CollectingAndReducing {
      * Compute the average age of the given list of Persons.
      */
     public static Double averageAge(List<Person> persons) {
-        return persons.stream()
-                .mapToInt(Person::getAge)
-                .average().getAsDouble();
-
+        return 0d;
     }
 
     /**
      * How old is the oldest person in the given list.
      */
     public static Integer maxAge(List<Person> persons) {
-        return persons.stream()
-                .mapToInt(Person::getAge)
-                .max().getAsInt();
+        return 0;
     }
 
     /**
      * Compute Age-Statistics (max, min, average, ...) for the given list of Persons.
      */
     public static IntSummaryStatistics ageStatistics(List<Person> persons) {
-        return persons.stream()
-                .mapToInt(Person::getAge)
-                .summaryStatistics();
+        return null;
     }
 
     /**
@@ -47,36 +40,28 @@ public static IntSummaryStatistics ageStatistics(List<Person> persons) {
      * Example-Result: "Maggie, Marge, Mary"
      */
     public static String buildCommaSeparatedListOfFirstNames(List<Person> persons) {
-        return persons.stream()
-                .map(Person::getFirstName)
-                .collect(Collectors.joining(", "));
+        return "";
     }
 
     /**
      * Identify the cheapest product (by pricePerUnit) in all invoices.
      */
     public static String cheapestProduct(List<Invoice> invoices) {
-        return invoices.stream()
-                .flatMap(invoice -> invoice.getItems().stream())
-                .min(Comparator.comparing(InvoiceItem::getPricePerUnit))
-                .get().getProduct();
+        return "";
     }
 
     /**
      * Identify the invoice with the highest total amount.
      */
     public static Invoice mostExpensiveInvoice(List<Invoice> invoices) {
-        return invoices.stream()
-                .collect(Collectors.<Invoice>maxBy(
-                        Comparator.comparing(Invoice::getTotal))).get();
+        return null;
     }
 
     /**
      * Just what the method name says.
      */
     public static Map<String, List<Invoice>> groupInvoicesByRecipient(List<Invoice> invoices) {
-        return invoices.stream()
-                .collect(Collectors.groupingBy(Invoice::getRecipient));
+        return Collections.emptyMap();
     }
 
     /**
@@ -85,25 +70,14 @@ public static Map<String, List<Invoice>> groupInvoicesByRecipient(List<Invoice>
      * Hint: Use the two-argument version of Collectors.groupingBy together with Collectors.mapping.
      */
     public static Map<String, BigDecimal> expensesByRecipient(List<Invoice> invoices) {
-        return invoices.stream()
-                .collect(Collectors.groupingBy(
-                        Invoice::getRecipient,
-                        Collectors.mapping(
-                                Invoice::getTotal,
-                                Collectors.reducing(
-                                        BigDecimal.ZERO,
-                                        (sum, elem) -> sum.add(elem)))));
+        return Collections.emptyMap();
     }
 
     /**
      * How many items of each product have been purchased?
      */
     public static Map<String, Integer> countByProduct(List<Invoice> invoices) {
-        return invoices.stream()
-                .flatMap(invoice -> invoice.getItems().stream())
-                .collect(Collectors.groupingBy(
-                        InvoiceItem::getProduct,
-                        Collectors.summingInt(InvoiceItem::getQuantity)));
+        return Collections.emptyMap();
     }
 
     /**
diff --git a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
index d87330a..719cb09 100644
--- a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
+++ b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
@@ -11,6 +11,7 @@
 import java.util.List;
 import java.util.Map;
 
+import static junit.framework.Assert.assertNotNull;
 import static org.hamcrest.Matchers.*;
 import static org.hamcrest.MatcherAssert.assertThat;
 
@@ -41,6 +42,7 @@ public void testMaxAge() throws Exception {
     @Test
     public void testAgeStatistics() throws Exception {
         IntSummaryStatistics statistic = CollectingAndReducing.ageStatistics(persons);
+        assertNotNull(statistic);
         assertThat(statistic.getAverage(), equalTo(30.571428571428573));
         assertThat(statistic.getCount(), equalTo(7l));
         assertThat(statistic.getMax(), equalTo(46));

From 05b2802c2ed035798d10583ad52846a6619768c3 Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Fri, 29 Nov 2013 14:10:07 +0100
Subject: [PATCH 12/23] Test for another task.

---
 .../streaming/CollectingAndReducingTest.java  | 23 +++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
index 719cb09..d77063d 100644
--- a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
+++ b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
@@ -1,15 +1,13 @@
 package de.codecentric.java8examples.streaming;
 
 import de.codecentric.java8examples.Invoice;
+import de.codecentric.java8examples.InvoiceItem;
 import de.codecentric.java8examples.Person;
 import de.codecentric.java8examples.TestData;
 import org.junit.Test;
 
 import java.math.BigDecimal;
-import java.util.Arrays;
-import java.util.IntSummaryStatistics;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 
 import static junit.framework.Assert.assertNotNull;
 import static org.hamcrest.Matchers.*;
@@ -109,7 +107,24 @@ public void testExpensesByRecipient() throws Exception {
 
     @Test
     public void testCountByProduct() throws Exception {
+        Map<String, Integer> expected = new HashMap<>();
+        for (Invoice invoice: invoices) {
+            for (InvoiceItem item: invoice.getItems()) {
+                String product = item.getProduct();
+                if (expected.get(product) == null) {
+                    expected.put(product, Integer.valueOf(0));
+                }
+                expected.put(
+                        product,
+                        expected.get(product) + item.getQuantity());
+            }
+        }
 
+        Map<String, Integer> actual = CollectingAndReducing.countByProduct(invoices);
+        assertThat(actual.keySet(), hasSize(expected.size()));
+        for (Map.Entry entry: expected.entrySet()) {
+            assertThat(actual, hasEntry(entry.getKey(), entry.getValue()));
+        }
     }
 
     @Test

From 6b2922dcdefb38e9933944ea8342f6823e78a2b5 Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Fri, 29 Nov 2013 14:18:22 +0100
Subject: [PATCH 13/23] Fix one test.

---
 .../java8examples/streaming/CollectingAndReducingTest.java     | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
index d77063d..10eb624 100644
--- a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
+++ b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
@@ -19,7 +19,6 @@
  */
 public class CollectingAndReducingTest {
     private List<Person> persons = TestData.listOfPersons();
-
     private List<Invoice> invoices = TestData.listOfInvoices();
     private List<String> recipients = Arrays.asList("Homer", "Bart", "Marge");
 
@@ -93,7 +92,7 @@ public void testGroupInvoicesByRecipient() throws Exception {
     public void testExpensesByRecipient() throws Exception {
         Map<String,BigDecimal> expencesByRecipient =
                 CollectingAndReducing.expensesByRecipient(invoices);
-        assertThat(expencesByRecipient.keySet(), hasSize(invoices.size()));
+        assertThat(expencesByRecipient.keySet(), hasSize(recipients.size()));
         for (String recipient: recipients) {
             BigDecimal expenses = BigDecimal.ZERO;
             for (Invoice invoice: invoices) {

From 6fb7af834175f27123c3d9c0e4e6395d5bc84c5b Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Fri, 29 Nov 2013 14:18:22 +0100
Subject: [PATCH 14/23] Fix one test.

---
 .../java8examples/streaming/CollectingAndReducingTest.java     | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
index d77063d..10eb624 100644
--- a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
+++ b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
@@ -19,7 +19,6 @@
  */
 public class CollectingAndReducingTest {
     private List<Person> persons = TestData.listOfPersons();
-
     private List<Invoice> invoices = TestData.listOfInvoices();
     private List<String> recipients = Arrays.asList("Homer", "Bart", "Marge");
 
@@ -93,7 +92,7 @@ public void testGroupInvoicesByRecipient() throws Exception {
     public void testExpensesByRecipient() throws Exception {
         Map<String,BigDecimal> expencesByRecipient =
                 CollectingAndReducing.expensesByRecipient(invoices);
-        assertThat(expencesByRecipient.keySet(), hasSize(invoices.size()));
+        assertThat(expencesByRecipient.keySet(), hasSize(recipients.size()));
         for (String recipient: recipients) {
             BigDecimal expenses = BigDecimal.ZERO;
             for (Invoice invoice: invoices) {

From 0604f8626e830630a72d07e81610dce9f5d76ec9 Mon Sep 17 00:00:00 2001
From: Daniel Reuter <daniel.reuter@codecentric.de>
Date: Fri, 29 Nov 2013 15:15:28 +0100
Subject: [PATCH 15/23] Fixed testdata

---
 .../java8examples/streaming/FilteringAndMappingTest.java       | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java b/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java
index ea28169..103723a 100644
--- a/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java
+++ b/src/test/java/de/codecentric/java8examples/streaming/FilteringAndMappingTest.java
@@ -54,6 +54,7 @@ public void extractFirstnamesWhereLastnameStartsWith() {
 
     @Test
     public void testExtractAllProducts() throws Exception {
-	MatcherAssert.assertThat(FilteringAndMapping.extractAllProducts(invoices), containsInAnyOrder("Beer", "Burrito", "Coke"));
+	MatcherAssert.assertThat(FilteringAndMapping.extractAllProducts(invoices),
+		containsInAnyOrder("Beer", "Burger", "Corn Flakes", "Chips", "Coke", "Cake", "Left-Handed Scissors"));
     }
 }

From 21ba27e8452167caed2d9924d264eae2b3e60ac7 Mon Sep 17 00:00:00 2001
From: Daniel Reuter <daniel.reuter@codecentric.de>
Date: Fri, 29 Nov 2013 15:27:59 +0100
Subject: [PATCH 16/23] Eclipse!

---
 .../java/de/codecentric/java8examples/Invoice.java     | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/src/main/java/de/codecentric/java8examples/Invoice.java b/src/main/java/de/codecentric/java8examples/Invoice.java
index bc82460..1f88105 100644
--- a/src/main/java/de/codecentric/java8examples/Invoice.java
+++ b/src/main/java/de/codecentric/java8examples/Invoice.java
@@ -4,6 +4,8 @@
 import java.util.List;
 import java.util.stream.Collectors;
 
+import sun.reflect.generics.reflectiveObjects.NotImplementedException;
+
 public class Invoice {
 
     private String sender;
@@ -23,13 +25,7 @@ public List<InvoiceItem> getItems() {
     }
 
     public BigDecimal getTotal() {
-        return getItems().stream()
-                .map(invoice -> invoice
-                        .getPricePerUnit()
-                        .multiply(BigDecimal.valueOf(invoice.getQuantity())))
-                .collect(Collectors.reducing(
-                        BigDecimal.ZERO,
-                        (sum, elem) -> sum.add(elem)));
+        throw new NotImplementedException();
     }
 
     public Invoice(String sender, String recipient, List<InvoiceItem> items) {

From 34cc0db8abec610c0e0749ba28da34bb66b4292d Mon Sep 17 00:00:00 2001
From: Daniel Reuter <daniel.reuter@codecentric.de>
Date: Fri, 29 Nov 2013 15:29:38 +0100
Subject: [PATCH 17/23] Solutions

---
 .../streaming/FilteringAndMapping.java        | 47 +++++++++++++------
 1 file changed, 32 insertions(+), 15 deletions(-)

diff --git a/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java b/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
index 25c8574..22be36b 100644
--- a/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
+++ b/src/main/java/de/codecentric/java8examples/streaming/FilteringAndMapping.java
@@ -1,13 +1,16 @@
 package de.codecentric.java8examples.streaming;
 
+import java.time.LocalDate;
+import java.time.Period;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
 import de.codecentric.java8examples.Invoice;
 import de.codecentric.java8examples.InvoiceItem;
 import de.codecentric.java8examples.Person;
 
-import java.util.Collections;
-import java.util.List;
-import java.util.Set;
-
 /**
  * Your task: Implement the following methods and make the tests passs.
  */
@@ -17,44 +20,58 @@ public class FilteringAndMapping {
      * Extract a list of names (firstname and lastname separated by space) from a given list of Person objects.
      */
     public static List<String> extractNames(List<Person> persons) {
-        return Collections.emptyList();
+	return persons.stream()//
+		.<String> map(p -> p.getFirstName() + " " + p.getLastName())//
+		.collect(Collectors.<String> toList());
     }
 
     /**
-     * Extract a sorted (ascending by lastname) list of names (firstname and lastname separated by space) from a
-     * given list of Person objects.
+     * Extract a sorted (ascending by lastname) list of names (firstname and lastname separated by space) from a given list of Person objects.
      */
     public static List<String> extractNamesSortedByLastname(List<Person> persons) {
-        return Collections.emptyList();
+	return persons.stream()//
+		.sorted((Person p1, Person p2) -> (p1.getLastName().compareTo(p2.getLastName())))//
+		.<String> map(p -> p.getFirstName() + " " + p.getLastName())//
+		.collect(Collectors.<String> toList());
     }
 
     /**
      * From a given list of Person objects, extract a list of female firstnames
      */
     public static List<String> extractFemaleFirstnames(List<Person> persons) {
-        return Collections.emptyList();
+	return persons.stream()//
+		.filter(p -> p.getGender().equals(Person.Gender.FEMALE))//
+		.<String> map(p -> p.getFirstName())//
+		.collect(Collectors.<String> toList());
     }
 
     /**
      * Extract all females older than 18 years from a given list of Person objects.
      */
     public static List<Person> extractAdultWomen(List<Person> persons) {
-        return Collections.emptyList();
+	return persons.stream()//
+		.filter(p -> p.getGender().equals(Person.Gender.FEMALE))//
+		.filter((Person p) -> Period.between(p.getBirthDay(), LocalDate.now()).getYears() >= 18)//
+		.collect(Collectors.<Person> toList());
     }
 
     /**
-     * From a given list of Person objects, extract a set of firstnames of the people whose lastname starts
-     * with the given string.
+     * From a given list of Person objects, extract a set of firstnames of the people whose lastname starts with the given string.
      */
     public static Set<String> extractFirstnamesWhereLastnameStartsWith(List<Person> persons, String startsWith) {
-        return Collections.emptySet();
+	return persons.stream()//
+		.filter((Person p) -> p.getLastName().startsWith(startsWith))//
+		.<String> map(p -> p.getFirstName())//
+		.collect(Collectors.<String> toSet());
     }
 
     /**
      * From a given list of invoices, extract a set of all product names.
      */
     public static Set<String> extractAllProducts(List<Invoice> invoices) {
-        return Collections.emptySet();
+	return invoices.stream()//
+		.<InvoiceItem> flatMap((Invoice i) -> i.getItems().stream())//
+		.<String> map((InvoiceItem i) -> i.getProduct())//
+		.collect(Collectors.<String> toSet());
     }
 }
-

From c9b6e26af2cee45e5c08101476ecafb1d69326b4 Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Wed, 4 Dec 2013 13:40:36 +0100
Subject: [PATCH 18/23] One more test

---
 .../streaming/CollectingAndReducing.java      | 32 ++++++++++++++++++-
 .../streaming/CollectingAndReducingTest.java  | 21 ++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
index ae6be2b..e6edb92 100644
--- a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
+++ b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
@@ -5,7 +5,9 @@
 import de.codecentric.java8examples.Person;
 
 import java.math.BigDecimal;
+import java.util.AbstractMap.SimpleEntry;
 import java.util.*;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 /**
@@ -91,7 +93,7 @@ public static Map<String, String> cheapestDealersByProduct(List<Invoice> invoice
     /**
      * From a given list of invoices, compute for every dealer the available products together with its price.
      */
-    public static Map<String, ProductWithPrice> computeDealerInventory(List<Invoice> invoices) {
+    public static Map<String, List<ProductWithPrice>> computeDealerInventory(List<Invoice> invoices) {
         return Collections.emptyMap();
     }
 
@@ -121,6 +123,34 @@ public String getProductName() {
         public BigDecimal getPrice() {
             return price;
         }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (o == null || getClass() != o.getClass()) return false;
+
+            ProductWithPrice that = (ProductWithPrice) o;
+
+            if (price != null ? !price.equals(that.price) : that.price != null) return false;
+            if (productName != null ? !productName.equals(that.productName) : that.productName != null) return false;
+
+            return true;
+        }
+
+        @Override
+        public int hashCode() {
+            int result = productName != null ? productName.hashCode() : 0;
+            result = 31 * result + (price != null ? price.hashCode() : 0);
+            return result;
+        }
+
+        @Override
+        public String toString() {
+            return "ProductWithPrice{" +
+                    "productName='" + productName + '\'' +
+                    ", price=" + price +
+                    '}';
+        }
     }
 
 }
diff --git a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
index 10eb624..6e93505 100644
--- a/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
+++ b/src/test/java/de/codecentric/java8examples/streaming/CollectingAndReducingTest.java
@@ -133,7 +133,28 @@ public void testCheapestDealersByProduct() throws Exception {
 
     @Test
     public void testComputeDealerInventory() throws Exception {
+        HashMap<String, List<CollectingAndReducing.ProductWithPrice>> expected = new HashMap<>();
+        for (Invoice invoice: invoices) {
+            String sender = invoice.getSender();
+            if (expected.get(sender) == null) {
+                expected.put(sender, new ArrayList<CollectingAndReducing.ProductWithPrice>());
+            }
+            List<CollectingAndReducing.ProductWithPrice> itemsOfSender = expected.get(sender);
+            for (InvoiceItem item: invoice.getItems()) {
+                CollectingAndReducing.ProductWithPrice newItem = new CollectingAndReducing.ProductWithPrice(item.getProduct(), item.getPricePerUnit());
+                if (!itemsOfSender.contains(newItem)) {
+                    itemsOfSender.add(newItem);
+                }
+            }
+        }
+
+        Map<String, List<CollectingAndReducing.ProductWithPrice>> actual =
+                CollectingAndReducing.computeDealerInventory(invoices);
 
+        assertThat(actual.keySet(), hasSize(expected.size()));
+        for (String sender: expected.keySet()) {
+            assertThat("Unexpected item set for dealer " + sender, actual.get(sender), containsInAnyOrder(expected.get(sender).toArray()));
+        }
     }
 
     @Test

From 3f8756aad5b30fbc45db023daf7a47b687f4c92f Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Wed, 4 Dec 2013 13:42:29 +0100
Subject: [PATCH 19/23] One more (crazy) solution.

---
 .../streaming/CollectingAndReducing.java      | 20 ++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
index 1d82e14..597e1dc 100644
--- a/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
+++ b/src/main/java/de/codecentric/java8examples/streaming/CollectingAndReducing.java
@@ -120,7 +120,25 @@ public static Map<String, String> cheapestDealersByProduct(List<Invoice> invoice
      * From a given list of invoices, compute for every dealer the available products together with its price.
      */
     public static Map<String, List<ProductWithPrice>> computeDealerInventory(List<Invoice> invoices) {
-        return Collections.emptyMap();
+        Function<SimpleEntry<String, ProductWithPrice>, String> classifier =
+                (SimpleEntry<String, ProductWithPrice> entry) -> (String) entry.getKey();
+        Function<SimpleEntry<String, ProductWithPrice>, ProductWithPrice> mapper =
+                (SimpleEntry<String, ProductWithPrice> entry) -> (ProductWithPrice) entry.getValue();
+
+        Map<String, List<Invoice>> invoicesBySender = invoices.stream()
+                .collect(Collectors.groupingBy(Invoice::getSender));
+        return invoicesBySender.entrySet().stream()
+                .<SimpleEntry<String, ProductWithPrice>>flatMap(entry -> entry.getValue().stream()
+                        .flatMap((Invoice invoice) -> invoice.getItems().stream())
+                        .map((InvoiceItem item) -> new SimpleEntry<String, ProductWithPrice>(
+                                entry.getKey(),
+                                new ProductWithPrice(item.getProduct(), item.getPricePerUnit()))))
+                .distinct()
+                .collect(Collectors.groupingBy(
+                        classifier,
+                        Collectors.mapping(
+                                mapper,
+                                Collectors.toList())));
     }
 
     /**

From cd7869469c8bb3fedd399ce9c9d933b5dfc1a8b9 Mon Sep 17 00:00:00 2001
From: Michael Lex <mich.lex@gmail.com>
Date: Wed, 4 Dec 2013 13:44:43 +0100
Subject: [PATCH 20/23] Revivive accidentally deleted method Invoice.getTotal.

---
 src/main/java/de/codecentric/java8examples/Invoice.java | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/main/java/de/codecentric/java8examples/Invoice.java b/src/main/java/de/codecentric/java8examples/Invoice.java
index 1f88105..b510a07 100644
--- a/src/main/java/de/codecentric/java8examples/Invoice.java
+++ b/src/main/java/de/codecentric/java8examples/Invoice.java
@@ -25,7 +25,13 @@ public List<InvoiceItem> getItems() {
     }
 
     public BigDecimal getTotal() {
-        throw new NotImplementedException();
+        return getItems().stream()
+            .<BigDecimal>map(invoice -> invoice
+                    .getPricePerUnit()
+                    .multiply(BigDecimal.valueOf(invoice.getQuantity())))
+            .collect(Collectors.reducing(
+                    BigDecimal.ZERO,
+                    (sum, elem) -> sum.add(elem)));
     }
 
     public Invoice(String sender, String recipient, List<InvoiceItem> items) {

From 1030082b968d593b06ec634851f2d4c67fcb7913 Mon Sep 17 00:00:00 2001
From: Benedikt Ritter <beneritter@gmail.com>
Date: Fri, 13 Dec 2013 13:16:09 +0100
Subject: [PATCH 21/23] JavaDoc for default method implementation

---
 .../java8examples/defaultmethods/GreetingService.java        | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/main/java/de/codecentric/java8examples/defaultmethods/GreetingService.java b/src/main/java/de/codecentric/java8examples/defaultmethods/GreetingService.java
index 16e4c6d..473dbd8 100644
--- a/src/main/java/de/codecentric/java8examples/defaultmethods/GreetingService.java
+++ b/src/main/java/de/codecentric/java8examples/defaultmethods/GreetingService.java
@@ -5,6 +5,11 @@
  */
 public interface GreetingService {
 
+    /**
+     * Creates a greeting message. The provided default implementation simply returns "Hello world!"
+     *
+     * @return A greeting message.
+     */
     default String greet() {
         return "Hello World!";
     }

From 206def815c1b9e54600678324e4d28bb65b622d3 Mon Sep 17 00:00:00 2001
From: Benedikt Ritter <beneritter@gmail.com>
Date: Fri, 13 Dec 2013 13:17:46 +0100
Subject: [PATCH 22/23] Add an example showing how to work with unrealted
 default methods

---
 .../CombinedGreetingService.java              | 20 +++++++++++++++++++
 .../defaultmethods/GreetingServiceTest.java   |  6 ++++++
 2 files changed, 26 insertions(+)
 create mode 100644 src/main/java/de/codecentric/java8examples/defaultmethods/CombinedGreetingService.java

diff --git a/src/main/java/de/codecentric/java8examples/defaultmethods/CombinedGreetingService.java b/src/main/java/de/codecentric/java8examples/defaultmethods/CombinedGreetingService.java
new file mode 100644
index 0000000..f8db072
--- /dev/null
+++ b/src/main/java/de/codecentric/java8examples/defaultmethods/CombinedGreetingService.java
@@ -0,0 +1,20 @@
+package de.codecentric.java8examples.defaultmethods;
+
+/**
+ * A greeting service implementation that inherits {@link #greet()} from two unrelated interfaces. It has to provide
+ * an implementation for {@code greet()}.
+ */
+public class CombinedGreetingService implements GreetingService, AlternativeGreetingService {
+
+    /**
+     * An implementation of the {@code greet()} method which is defined in both, {@link GreetingService} and
+     * {@link AlternativeGreetingService}. This implementation simply delegates to the default {@code greet()}
+     * implementation of the {@code GreetingService} interface
+     *
+     * @return the result of calling {@link GreetingService#greet()}.
+     */
+    @Override
+    public String greet() {
+        return GreetingService.super.greet();
+    }
+}
diff --git a/src/test/java/de/codecentric/java8examples/defaultmethods/GreetingServiceTest.java b/src/test/java/de/codecentric/java8examples/defaultmethods/GreetingServiceTest.java
index 7e3d72e..81a5ee1 100644
--- a/src/test/java/de/codecentric/java8examples/defaultmethods/GreetingServiceTest.java
+++ b/src/test/java/de/codecentric/java8examples/defaultmethods/GreetingServiceTest.java
@@ -23,4 +23,10 @@ public void greetFromExtended() throws Exception {
     public void greetFromDerived() throws Exception {
         assertEquals("Salut le monde!", new DerivedGreetingService().greet());
     }
+
+    @Test
+    public void testName() throws Exception {
+        assertEquals("Hello World!", new CombinedGreetingService().greet());
+
+    }
 }

From c6ed53948203dc52aa146928b8f4c06063f0ae78 Mon Sep 17 00:00:00 2001
From: Benedikt Ritter <beneritter@gmail.com>
Date: Fri, 13 Dec 2013 13:20:34 +0100
Subject: [PATCH 23/23] Add example for using a method reference to implemente
 a function

---
 .../de/codecentric/java8examples/lambdas/LambdaExampleTest.java | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java b/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java
index 3feb748..3d7dd1d 100644
--- a/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java
+++ b/src/test/java/de/codecentric/java8examples/lambdas/LambdaExampleTest.java
@@ -60,6 +60,8 @@ public void peterIsOlderThan30WithTypeInference() throws Exception {
     public void getAgeFromWrappedElementViaFunctionApplication() throws Exception {
         // type is inferred from context
         assertEquals("Parker", example.apply(p -> p.getLastName()));
+        // different notation using a method reference
+        assertEquals("Parker", example.apply(Person::getLastName));
     }
 
     @Test