From 0adb3fe39ec01a412b848a2f5ed42044c4762959 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 12:32:56 +0800
Subject: [PATCH 01/20] Committed on or around 2023/10/01

---
 .../Super_Class_References_and_Subclass_Objects.java            | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Chapter7/theoretical/Super_Class_References_and_Subclass_Objects.java b/Chapter7/theoretical/Super_Class_References_and_Subclass_Objects.java
index 0905f5e..9bc860a 100644
--- a/Chapter7/theoretical/Super_Class_References_and_Subclass_Objects.java
+++ b/Chapter7/theoretical/Super_Class_References_and_Subclass_Objects.java
@@ -86,7 +86,7 @@ public Triangle_2(String s, double w, double h) {
 	}
 	
 	Triangle_2(Triangle_2 ob){
-		
+		super(ob);
 	}
 	
 	

From 52fa5931c0ac2f8433f21e0b02522760cb85fc4b Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 14:04:13 +0800
Subject: [PATCH 02/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo.java | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 Chapter8/Interface/Series_Demo.java

diff --git a/Chapter8/Interface/Series_Demo.java b/Chapter8/Interface/Series_Demo.java
new file mode 100644
index 0000000..528be3b
--- /dev/null
+++ b/Chapter8/Interface/Series_Demo.java
@@ -0,0 +1,15 @@
+package Interface;
+
+// An interface specifies what must be done, but not how to do it.
+interface Series2{
+	
+}
+
+public class Series_Demo {
+
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+
+	}
+
+}

From 54ff00d98c34225e026a4f22dbb027f068d9d04b Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 14:34:16 +0800
Subject: [PATCH 03/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo.java | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Chapter8/Interface/Series_Demo.java b/Chapter8/Interface/Series_Demo.java
index 528be3b..69e82a7 100644
--- a/Chapter8/Interface/Series_Demo.java
+++ b/Chapter8/Interface/Series_Demo.java
@@ -3,6 +3,9 @@
 // An interface specifies what must be done, but not how to do it.
 interface Series2{
 	
+	int getNext();
+	void reset();
+	void setStart(int x);
 }
 
 public class Series_Demo {

From 0a4b2f79b079b8212cffb61e247c0e5c20d260bd Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 14:53:52 +0800
Subject: [PATCH 04/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo.java | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/Chapter8/Interface/Series_Demo.java b/Chapter8/Interface/Series_Demo.java
index 69e82a7..8664625 100644
--- a/Chapter8/Interface/Series_Demo.java
+++ b/Chapter8/Interface/Series_Demo.java
@@ -8,10 +8,26 @@ interface Series2{
 	void setStart(int x);
 }
 
+
+// Implement Series.
+class ByTwos implements Series2{
+	int start; 
+	int value;
+	
+	public ByTwos() {
+		start = 0;
+		value = 0;
+	}
+	
+	int getNext() {
+		
+	}
+}
+
 public class Series_Demo {
 
 	public static void main(String[] args) {
-		// TODO Auto-generated method stub
+		
 
 	}
 

From c6c5d419f2ea1fa8884e506862c50d3afbe05850 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 14:59:10 +0800
Subject: [PATCH 05/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo.java | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Chapter8/Interface/Series_Demo.java b/Chapter8/Interface/Series_Demo.java
index 8664625..efd189c 100644
--- a/Chapter8/Interface/Series_Demo.java
+++ b/Chapter8/Interface/Series_Demo.java
@@ -19,8 +19,9 @@ public ByTwos() {
 		value = 0;
 	}
 	
-	int getNext() {
-		
+	public int getNext() {
+		value += 2;
+		return value;
 	}
 }
 

From edac15bb2a03547b7f3984ec64a714a64e8fbba2 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 15:02:16 +0800
Subject: [PATCH 06/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo.java | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Chapter8/Interface/Series_Demo.java b/Chapter8/Interface/Series_Demo.java
index efd189c..d5b3774 100644
--- a/Chapter8/Interface/Series_Demo.java
+++ b/Chapter8/Interface/Series_Demo.java
@@ -19,10 +19,16 @@ public ByTwos() {
 		value = 0;
 	}
 	
+	// Whenever you implement a method defined by an interface, it must be implemented as public; 
+	// because all members of an interface are implicitly public.
 	public int getNext() {
 		value += 2;
 		return value;
 	}
+	
+	public void reset() {
+		value = start;
+	}
 }
 
 public class Series_Demo {

From 7578b79bb9b0b01a56c02dcb35ea90d36c869e7e Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 15:05:44 +0800
Subject: [PATCH 07/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo.java | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Chapter8/Interface/Series_Demo.java b/Chapter8/Interface/Series_Demo.java
index d5b3774..f1e3096 100644
--- a/Chapter8/Interface/Series_Demo.java
+++ b/Chapter8/Interface/Series_Demo.java
@@ -10,11 +10,11 @@ interface Series2{
 
 
 // Implement Series.
-class ByTwos implements Series2{
+class ByTwos2 implements Series2{
 	int start; 
 	int value;
 	
-	public ByTwos() {
+	public ByTwos2() {
 		start = 0;
 		value = 0;
 	}
@@ -29,6 +29,12 @@ public int getNext() {
 	public void reset() {
 		value = start;
 	}
+
+	@Override
+	public void setStart(int x) {
+		// TODO Auto-generated method stub
+		
+	}
 }
 
 public class Series_Demo {

From 6cf437d86b708cfca2fef5e17f7f21a23c97f6be Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 15:24:31 +0800
Subject: [PATCH 08/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo.java | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Chapter8/Interface/Series_Demo.java b/Chapter8/Interface/Series_Demo.java
index f1e3096..d31797b 100644
--- a/Chapter8/Interface/Series_Demo.java
+++ b/Chapter8/Interface/Series_Demo.java
@@ -32,7 +32,9 @@ public void reset() {
 
 	@Override
 	public void setStart(int x) {
-		// TODO Auto-generated method stub
+		
+		start = x;
+		value = x;
 		
 	}
 }

From 515a00cdd187e1e04f1726c7e5a81ee4be3f9ef3 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 16:01:59 +0800
Subject: [PATCH 09/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo.java  |  1 +
 Chapter8/Interface/Series_Demo2.java | 58 ++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 Chapter8/Interface/Series_Demo2.java

diff --git a/Chapter8/Interface/Series_Demo.java b/Chapter8/Interface/Series_Demo.java
index d31797b..646bf15 100644
--- a/Chapter8/Interface/Series_Demo.java
+++ b/Chapter8/Interface/Series_Demo.java
@@ -43,6 +43,7 @@ public class Series_Demo {
 
 	public static void main(String[] args) {
 		
+		ByTwos2 oByTwos2 = new ByTwos2();
 
 	}
 
diff --git a/Chapter8/Interface/Series_Demo2.java b/Chapter8/Interface/Series_Demo2.java
new file mode 100644
index 0000000..ff4ddd3
--- /dev/null
+++ b/Chapter8/Interface/Series_Demo2.java
@@ -0,0 +1,58 @@
+package Interface;
+
+//An interface specifies what must be done, but not how to do it.
+interface Series3{
+	
+	int getNext();
+	void reset();
+	void setStart(int x);
+}
+
+
+//Implement Series.
+class ByTwos3 implements Series3{
+	int start; 
+	int value;
+	int previous;
+	
+	public ByTwos3() {
+		start = 0;
+		value = 0;
+	}
+	
+	ByTwos3(int previous) {
+		
+		this.previous = previous;
+		
+		start = 0;
+		value = 0;
+	}
+	
+	// Whenever you implement a method defined by an interface, it must be implemented as public; 
+	// because all members of an interface are implicitly public.
+	public int getNext() {
+		value += 2;
+		return value;
+	}
+	
+	public void reset() {
+		value = start;
+	}
+
+	@Override
+	public void setStart(int x) {
+		
+		start = x;
+		value = x;
+		
+	}
+}
+
+public class Series_Demo2 {
+
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+
+	}
+
+}

From c58c31c3b183f947fd5fd98926986ab35290d5cb Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 16:09:53 +0800
Subject: [PATCH 10/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo2.java | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Chapter8/Interface/Series_Demo2.java b/Chapter8/Interface/Series_Demo2.java
index ff4ddd3..5225b89 100644
--- a/Chapter8/Interface/Series_Demo2.java
+++ b/Chapter8/Interface/Series_Demo2.java
@@ -46,6 +46,10 @@ public void setStart(int x) {
 		value = x;
 		
 	}
+	
+	int getPrevious() {
+		return previous;
+	}
 }
 
 public class Series_Demo2 {

From 1ca38ce735700ad698dfefdcb427ffcfa6c0d4d4 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 16:29:01 +0800
Subject: [PATCH 11/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo2.java | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Chapter8/Interface/Series_Demo2.java b/Chapter8/Interface/Series_Demo2.java
index 5225b89..df2b91f 100644
--- a/Chapter8/Interface/Series_Demo2.java
+++ b/Chapter8/Interface/Series_Demo2.java
@@ -56,6 +56,8 @@ public class Series_Demo2 {
 
 	public static void main(String[] args) {
 		// TODO Auto-generated method stub
+		
+		ByTwos3 obByTwos3 = new ByTwos3(9);
 
 	}
 

From e8d7a68b9b4110b7278d52e0497028b7e45deb53 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 16:38:07 +0800
Subject: [PATCH 12/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo.java | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/Chapter8/Interface/Series_Demo.java b/Chapter8/Interface/Series_Demo.java
index 646bf15..8e259e4 100644
--- a/Chapter8/Interface/Series_Demo.java
+++ b/Chapter8/Interface/Series_Demo.java
@@ -44,6 +44,27 @@ public class Series_Demo {
 	public static void main(String[] args) {
 		
 		ByTwos2 oByTwos2 = new ByTwos2();
+		
+		for (int i = 0; i < 5; i++) {
+			
+			System.out.println("Next value is " + oByTwos2.getNext());
+		}
+		
+		System.out.println("\nResetting");
+		
+		oByTwos2.reset();
+		
+		for (int i = 0; i < 5; i++) {
+			System.out.println("Next value is " + oByTwos2.getNext());
+		}
+		
+		System.out.println("\nStarting at 100");
+		
+		oByTwos2.setStart(100);
+		
+		for (int i = 0; i < 5; i++) {
+			System.out.println("Next value is " + oByTwos2.getNext());
+		}
 
 	}
 

From ecfc002dc054ba9c9ebd7dbe171b098b11f2b516 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 17:48:17 +0800
Subject: [PATCH 13/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo2.java | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/Chapter8/Interface/Series_Demo2.java b/Chapter8/Interface/Series_Demo2.java
index df2b91f..1c31a27 100644
--- a/Chapter8/Interface/Series_Demo2.java
+++ b/Chapter8/Interface/Series_Demo2.java
@@ -58,6 +58,27 @@ public static void main(String[] args) {
 		// TODO Auto-generated method stub
 		
 		ByTwos3 obByTwos3 = new ByTwos3(9);
+		
+		
+		for (int i = 0; i < 5; i++) {
+			System.out.println("Next value is " + obByTwos3.getNext());
+		}
+		
+		System.out.println("\nResetting");
+		
+		obByTwos3.reset();
+		
+		for (int i = 0; i < 5; i++) {
+			System.out.println("Next value is " + obByTwos3.getNext());
+		}
+		
+		System.out.println("\n Starting at 100");
+		obByTwos3.setStart(100);
+		
+		for (int i = 0; i < 5; i++) {
+			
+			System.out.println("Next value is " + obByTwos3.getNext());
+		}
 
 	}
 

From d0727c948f3850040faa277e8317f1796b7e8c4a Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 17:49:54 +0800
Subject: [PATCH 14/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo2.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Chapter8/Interface/Series_Demo2.java b/Chapter8/Interface/Series_Demo2.java
index 1c31a27..6fac31c 100644
--- a/Chapter8/Interface/Series_Demo2.java
+++ b/Chapter8/Interface/Series_Demo2.java
@@ -72,7 +72,7 @@ public static void main(String[] args) {
 			System.out.println("Next value is " + obByTwos3.getNext());
 		}
 		
-		System.out.println("\n Starting at 100");
+		System.out.println("\nStarting at 100");
 		obByTwos3.setStart(100);
 		
 		for (int i = 0; i < 5; i++) {

From e19b2e648f2df64a39c00da4dfdd414c4ebd3584 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 18:13:59 +0800
Subject: [PATCH 15/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Series_Demo2.java | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Chapter8/Interface/Series_Demo2.java b/Chapter8/Interface/Series_Demo2.java
index 6fac31c..cc89a73 100644
--- a/Chapter8/Interface/Series_Demo2.java
+++ b/Chapter8/Interface/Series_Demo2.java
@@ -73,6 +73,7 @@ public static void main(String[] args) {
 		}
 		
 		System.out.println("\nStarting at 100");
+		
 		obByTwos3.setStart(100);
 		
 		for (int i = 0; i < 5; i++) {

From 3eb8547e330055a705c37fbb4945ec252d16f776 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 18:35:26 +0800
Subject: [PATCH 16/20] Committed on or around 2023/10/01

---
 .../Interface/Implementing_Interfaces.java    | 96 +++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 Chapter8/Interface/Implementing_Interfaces.java

diff --git a/Chapter8/Interface/Implementing_Interfaces.java b/Chapter8/Interface/Implementing_Interfaces.java
new file mode 100644
index 0000000..54d03da
--- /dev/null
+++ b/Chapter8/Interface/Implementing_Interfaces.java
@@ -0,0 +1,96 @@
+package Interface;
+
+//An interface specifies what must be done, but not how to get it done.
+interface Series4{
+	
+	int getNext();
+	void reset();
+	void setStart(int x);
+}
+
+
+//Implement Series.
+class ByTwos2_ implements Series4{
+	
+	// It's both permissible and common for classes that implement interfaces to define additional members 
+	// of their own.  (It absolutely is.  Without it, how to implement methods in an interface?)
+	int start; 
+	int value;
+	
+	public ByTwos2_() {
+		start = 0;
+		value = 0;
+	}
+	
+	// Whenever you implement a method defined by an interface, it must be implemented as public; 
+	// because all members of an interface are implicitly public.
+	public int getNext() {
+		value += 2;
+		return value;
+	}
+	
+	public void reset() {
+		value = start;
+	}
+
+	@Override
+	public void setStart(int x) {
+		
+		start = x;
+		value = x;
+		
+	}
+}
+
+
+class ByTwos4 implements Series4{
+	int start; 
+	int value;
+	int previous;
+	
+	public ByTwos4() {
+		start = 0;
+		value = 0;
+	}
+	
+	ByTwos4(int previous) {
+		
+		this.previous = previous;
+		
+		start = 0;
+		value = 0;
+	}
+	
+	// Whenever you implement a method defined by an interface, it must be implemented as public; 
+	// because all members of an interface are implicitly public.
+	public int getNext() {
+		value += 2;
+		return value;
+	}
+	
+	public void reset() {
+		value = start;
+	}
+
+	@Override
+	public void setStart(int x) {
+		
+		start = x;
+		value = x;
+		
+	}
+	
+	int getPrevious() {
+		return previous;
+	}
+}
+
+
+public class Implementing_Interfaces {
+
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+
+	}
+
+}

From 2eeb18cb0eeb924ad2a22b3de68483ece0c67abd Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 18:46:00 +0800
Subject: [PATCH 17/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Implementing_Interfaces.java | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Chapter8/Interface/Implementing_Interfaces.java b/Chapter8/Interface/Implementing_Interfaces.java
index 54d03da..23f6a67 100644
--- a/Chapter8/Interface/Implementing_Interfaces.java
+++ b/Chapter8/Interface/Implementing_Interfaces.java
@@ -80,6 +80,8 @@ public void setStart(int x) {
 		
 	}
 	
+	// Even though the interface does not define this method, it's both permissible and common for classes 
+	// that implement interfaces to define additional members of their own.
 	int getPrevious() {
 		return previous;
 	}

From b1c1432492613cd605472af57b57ce7df08226b9 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 18:59:30 +0800
Subject: [PATCH 18/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Implementing_Interfaces.java | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Chapter8/Interface/Implementing_Interfaces.java b/Chapter8/Interface/Implementing_Interfaces.java
index 23f6a67..043576b 100644
--- a/Chapter8/Interface/Implementing_Interfaces.java
+++ b/Chapter8/Interface/Implementing_Interfaces.java
@@ -88,6 +88,18 @@ int getPrevious() {
 }
 
 
+class ByThrees implements Series4{ // implement Series in a different way.
+	int start;
+	int value;
+	
+	public ByThrees() {
+		// TODO Auto-generated constructor stub
+		start = 0;
+		value = 0;
+	}
+}
+
+
 public class Implementing_Interfaces {
 
 	public static void main(String[] args) {

From 7b4d2e1fd68edcbef0ba256ae827ba414ad45eb5 Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 19:03:37 +0800
Subject: [PATCH 19/20] Committed on or around 2023/10/01

---
 Chapter8/Interface/Implementing_Interfaces.java | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/Chapter8/Interface/Implementing_Interfaces.java b/Chapter8/Interface/Implementing_Interfaces.java
index 043576b..9fb1e33 100644
--- a/Chapter8/Interface/Implementing_Interfaces.java
+++ b/Chapter8/Interface/Implementing_Interfaces.java
@@ -92,11 +92,25 @@ class ByThrees implements Series4{ // implement Series in a different way.
 	int start;
 	int value;
 	
-	public ByThrees() {
+	ByThrees() {
 		// TODO Auto-generated constructor stub
 		start = 0;
 		value = 0;
 	}
+	
+	public int getNext() {
+		value += 3;
+		return value;
+	}
+	
+	public void reset() {
+		value = start;
+	}
+	
+	public void setStart(int x) {
+		start = x;
+		value = x;
+	}
 }
 
 

From a82c06858ead9fef73703a3d831ceaeb3993782f Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Sun, 1 Oct 2023 19:28:08 +0800
Subject: [PATCH 20/20] Committed on or around 2023/10/01

---
 .../Interface/Implementing_Interfaces.java    | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/Chapter8/Interface/Implementing_Interfaces.java b/Chapter8/Interface/Implementing_Interfaces.java
index 9fb1e33..905d08e 100644
--- a/Chapter8/Interface/Implementing_Interfaces.java
+++ b/Chapter8/Interface/Implementing_Interfaces.java
@@ -1,5 +1,7 @@
 package Interface;
 
+import Cpp.this_keyword;
+
 //An interface specifies what must be done, but not how to get it done.
 interface Series4{
 	
@@ -88,11 +90,11 @@ int getPrevious() {
 }
 
 
-class ByThrees implements Series4{ // implement Series in a different way.
+class ByThrees2 implements Series4{ // implement Series in a different way.
 	int start;
 	int value;
 	
-	ByThrees() {
+	ByThrees2() {
 		// TODO Auto-generated constructor stub
 		start = 0;
 		value = 0;
@@ -114,6 +116,19 @@ public void setStart(int x) {
 }
 
 
+// If a class includes an interface but does not fully implement the methods defined by that interface, then
+// that class must be declared as abstract.
+abstract class implicate implements Series4{
+	
+	int start;
+	
+	public void setStart(int start) {
+		this.start = start;
+	}
+	
+}
+
+
 public class Implementing_Interfaces {
 
 	public static void main(String[] args) {