diff --git a/ch11/.checkstyle b/ch11/.checkstyle
deleted file mode 100644
index 744b9f9..0000000
--- a/ch11/.checkstyle
+++ /dev/null
@@ -1,8 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-
-<fileset-config file-format-version="1.2.0" simple-config="true" sync-formatter="false">
-  <fileset name="all" enabled="true" check-config-name="ThinkJavaCode2" local="false">
-    <file-match-pattern match-pattern="." include-pattern="true"/>
-  </fileset>
-  <filter name="UnOpenedFiles" enabled="true"/>
-</fileset-config>
diff --git a/ch11/.classpath b/ch11/.classpath
deleted file mode 100644
index 3f3893a..0000000
--- a/ch11/.classpath
+++ /dev/null
@@ -1,6 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<classpath>
-	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
-	<classpathentry kind="src" path=""/>
-	<classpathentry kind="output" path=""/>
-</classpath>
diff --git a/ch11/.project b/ch11/.project
deleted file mode 100644
index dd4d0e0..0000000
--- a/ch11/.project
+++ /dev/null
@@ -1,23 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<projectDescription>
-	<name>ch11</name>
-	<comment></comment>
-	<projects>
-	</projects>
-	<buildSpec>
-		<buildCommand>
-			<name>org.eclipse.jdt.core.javabuilder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-		<buildCommand>
-			<name>net.sf.eclipsecs.core.CheckstyleBuilder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
-	</buildSpec>
-	<natures>
-		<nature>org.eclipse.jdt.core.javanature</nature>
-		<nature>net.sf.eclipsecs.core.CheckstyleNature</nature>
-	</natures>
-</projectDescription>
diff --git a/ch11/Time.java b/ch11/Time.java
deleted file mode 100644
index fe5bfd6..0000000
--- a/ch11/Time.java
+++ /dev/null
@@ -1,115 +0,0 @@
-/**
- * Represents a time of day.
- */
-public class Time {
-
-    private int hour;
-    private int minute;
-    private double second;
-
-    /**
-     * Construct a Time object with default values.
-     */
-    public Time() {
-        this.hour = 0;
-        this.minute = 0;
-        this.second = 0.0;
-    }
-
-    /**
-     * Construct a Time object with given values.
-     */
-    public Time(int hour, int minute, double second) {
-        this.hour = hour;
-        this.minute = minute;
-        this.second = second;
-    }
-
-    public int getHour() {
-        return this.hour;
-    }
-
-    public int getMinute() {
-        return this.minute;
-    }
-
-    public double getSecond() {
-        return this.second;
-    }
-
-    public void setHour(int hour) {
-        this.hour = hour;
-    }
-
-    public void setMinute(int minute) {
-        this.minute = minute;
-    }
-
-    public void setSecond(double second) {
-        this.second = second;
-    }
-
-    /**
-     * Prints the time in a simple format.
-     */
-    public static void printTime(Time t) {
-        System.out.print(t.hour);
-        System.out.print(":");
-        System.out.println(t.minute);
-        System.out.print(":");
-        System.out.println(t.second);
-    }
-
-    /**
-     * Returns a String representation of the time.
-     */
-    public String toString() {
-        return String.format("%02d:%02d:%04.1f\n",
-            this.hour, this.minute, this.second);
-    }
-
-    /**
-     * Tests whether two times are equivalent.
-     */
-    public boolean equals(Time that) {
-        final double DELTA = 0.001;
-        return this.hour == that.hour
-            && this.minute == that.minute
-            && Math.abs(this.second - that.second) < DELTA;
-    }
-
-    /**
-     * Adds two Times and returns a new Time object (static method).
-     */
-    public static Time add(Time t1, Time t2) {
-        Time sum = new Time();
-        sum.hour = t1.hour + t2.hour;
-        sum.minute = t1.minute + t2.minute;
-        sum.second = t1.second + t2.second;
-        return sum;
-    }
-
-    /**
-     * Adds two Times and returns a new Time object (instance method).
-     */
-    public Time add(Time t2) {
-        Time sum = new Time();
-        sum.hour = this.hour + t2.hour;
-        sum.minute = this.minute + t2.minute;
-        sum.second = this.second + t2.second;
-
-        if (sum.second >= 60.0) {
-            sum.second -= 60.0;
-            sum.minute += 1;
-        }
-        if (sum.minute >= 60) {
-            sum.minute -= 60;
-            sum.hour += 1;
-        }
-        if (sum.hour >= 24) {
-            sum.hour -= 24;
-        }
-        return sum;
-    }
-
-}
diff --git a/ch11/TimeClient.java b/ch11/TimeClient.java
deleted file mode 100644
index aa90401..0000000
--- a/ch11/TimeClient.java
+++ /dev/null
@@ -1,33 +0,0 @@
-/**
- * Class that uses Time objects.
- */
-public class TimeClient {
-
-    public static void main(String[] args) {
-        Time time = new Time(11, 59, 59.9);
-        System.out.println(time);
-
-        // cannot access private variables from another class
-        // System.out.println(time.hour);
-
-        String s = time.toString();
-        System.out.println(s);
-
-        Time time1 = new Time(9, 30, 0.0);
-        Time time2 = time1;
-        Time time3 = new Time(9, 30, 0.0);
-
-        System.out.println(time1 == time2);
-        System.out.println(time1 == time3);
-        System.out.println(time1.equals(time2));
-        System.out.println(time1.equals(time3));
-
-        Time startTime = new Time(18, 50, 0.0);
-        Time runningTime = new Time(2, 16, 0.0);
-        Time endTime = Time.add(startTime, runningTime);
-
-        // using the instance method
-        endTime = startTime.add(runningTime);
-    }
-
-}