What is Abstract Class in Java With Example | Full Stack With Java

Abstract Class In Java With Example | Full Stack With Java Course by Pankaj Sir

Abstract Class in Java :

1. An Abstract Class Can Consist of Both Complete and incomplete Methods.
2. An Abstract Class Can Consist of Static and non-Static Members.
3. An Abstract Class is Zero to 100% incomplete.
4. An Abstract Class Can Consist of Main Method.
5. Object of abstract Class can not be Created but Reference Variable of abstract Class Can be Created.

Example 1

public abstract class A {
public void test1() {   // correct
}
public void test2(); // Error
public abstract void test3();  // correct
}

• What is Interface in Java With Example
• What is Lambdas Expression in Java 8 With Example

Example 2

public abstract class A {
abstract public void test();
}

public class B extends A {
@Override
public void test(){
System.out.println(20);
}
public static void main ( String[] args ){
B b1 = new B();
b1.test();
}
}

Output : 20

Very Important Point of An Abstract Class

1. Abstract Class does Not Support Multiple Inheritance.

Example 3

public abstract class A {
}
public abstract class B {
}
public abstract class C extends A,B {  // Error
}

2. interface to Class and interface to abstract class Allowed but class to interface and abstract class to interface not Allowed

Example 4

public interface A {
public void test();
}
public abstract class B implements A {
}
public class C extends B {
@Override 
public void test() {
System.out.println(100);
}
public static void main( String[] args ) {
C c1 =  new C();
c1.test();
}
}

Output : 100

Difference Between Abstract Class and Interface