Types of inheritance:
On the basis of class, there can be three types of inheritance in java: single, multilevel and hierarchical.
Single Inheritance:
When a class inherits another class, it is known as a single inheritance.
Sample Program:
CLASS A PROGRAM:
package x.ab;
public class A
{
public static void main(String[]args)
{
}
public void methodA()
{
System.out.println(“Base Class Method”);
}
}
CLASS B PROGRAM:
package x.ab;
public class B extends A
{
public static void main(String[]args)
{
B obj = new B();
obj.methodA();
obj.methodB();
}
public void methodB()
{
System.out.println(“Child Class Method”);
}
}
OUTPUT:
- c:\java>javac -d . A.java
- c:\java>javac -d . B.java
- c:\java>java x.ab.B
Base Class Method
Child Class Method
Multilevel inheritance:
When a class extends a class, which extends anther class then this is called multilevel inheritance.
Sample Program:
CLASS A PROGRAM:
package x.ab;
public class A
{
public static void main(String[]args)
{
}
public void methodA()
{
System.out.println(“Base Class Method”);
}
}
CLASS B PROGRAM:
package x.ab;
public class B extends A
{
public static void main(String[]args)
{
//B obj = new B();
//obj.methodA();
//obj.methodB();
}
public void methodB()
{
System.out.println(“Child Class Method”);
}
}
Class C PROGRAM:
package x.ab;
public class C extends B
{
public static void main(String[]args)
{
C obj = new C();
obj.methodA();
obj.methodB();
obj.methodC();
}
public void methodC()
{
System.out.println(“New Child Class Method”);
}
}
OUTPUT:
- c:\java>javac -d . C.java
- c:\java>java x.ab.C
Base Class Method
Child Class Method
New Child Class Method
Hierarchical Inheritance:
In Hierarchical Inheritance, one class is inherited by many sub classes.
Method Overriding:
If subclass (child class) has the same method as declared in the parent class, it is known as method overriding in Java.
Usage of Java Method Overriding:
- Method overriding is used to provide the specific implementation of a method which is already provided by its superclass.
- Method overriding is used for runtime polymorphism.
Rules for Java Method Overriding:
- The method must have the same name as in the parent class
- The method must have the same parameter as in the parent class.
- There must be an IS-A relationship (inheritance).
SAMPLE PROGRAM:
package x.ab;
public class C extends B
{
public static void main(String[]args)
{
C obj = new C();
B object = new B();
object.methodB();
object.methodA();
obj.methodB();
obj.methodC();
}
public void methodC()
{
System.out.println(“New Child Class Method”);
}
public void methodB()
{
System.out.println(“FIRST CHILD CLASS METHOD”);
}
}
OUTPUT:
- c:\java>javac -d . C.java
- c:\java>java x.ab.C
Child Class Method
Base Class Method
FIRST CHILD CLASS METHOD
New Child Class Method
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