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);
 	}
 	
 	
diff --git a/Chapter8/Interface/Implementing_Interfaces.java b/Chapter8/Interface/Implementing_Interfaces.java
new file mode 100644
index 0000000..905d08e
--- /dev/null
+++ b/Chapter8/Interface/Implementing_Interfaces.java
@@ -0,0 +1,139 @@
+package Interface;
+
+import Cpp.this_keyword;
+
+//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;
+		
+	}
+	
+	// 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;
+	}
+}
+
+
+class ByThrees2 implements Series4{ // implement Series in a different way.
+	int start;
+	int value;
+	
+	ByThrees2() {
+		// 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;
+	}
+}
+
+
+// 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) {
+		// TODO Auto-generated method stub
+
+	}
+
+}
diff --git a/Chapter8/Interface/Series_Demo.java b/Chapter8/Interface/Series_Demo.java
new file mode 100644
index 0000000..8e259e4
--- /dev/null
+++ b/Chapter8/Interface/Series_Demo.java
@@ -0,0 +1,71 @@
+package Interface;
+
+// An interface specifies what must be done, but not how to do it.
+interface Series2{
+	
+	int getNext();
+	void reset();
+	void setStart(int x);
+}
+
+
+// Implement Series.
+class ByTwos2 implements Series2{
+	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;
+		
+	}
+}
+
+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());
+		}
+
+	}
+
+}
diff --git a/Chapter8/Interface/Series_Demo2.java b/Chapter8/Interface/Series_Demo2.java
new file mode 100644
index 0000000..cc89a73
--- /dev/null
+++ b/Chapter8/Interface/Series_Demo2.java
@@ -0,0 +1,86 @@
+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;
+		
+	}
+	
+	int getPrevious() {
+		return previous;
+	}
+}
+
+public class Series_Demo2 {
+
+	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("\nStarting at 100");
+		
+		obByTwos3.setStart(100);
+		
+		for (int i = 0; i < 5; i++) {
+			
+			System.out.println("Next value is " + obByTwos3.getNext());
+		}
+
+	}
+
+}