Difference between Interface and Abstract Class

Difference Between Interface and Abstract Class

Interface	Abstract Class
An interface is an unimplemented class.	An abstract class is an incomplete class.
All methods are by default public abstract.	An abstract class can have both abstract and non abstract methods.
All variables by default public static final by default	Variables may be static final or may not be.
They cannot have any implemented methods.	They can have any number of  implemented methods.
An interface must be implemented by the base class.	An abstract class must be extended by the base class.
You need to override each method of an interface in the sub class.	You need to override abstract methods only.
An interface cannot have a constructor	An abstract class can have a constructor.
An interface can extend more than one interfaces.	An abstract class can implement more than one interface.

Point To Remember

• Object of both an interface and an abstract class can not be made.
• An abstract class may not override all methods of an interface.
• An abstract class may not override any method of another abstract class.
• An abstract method in interface or abstract class can not be static.

Example : Use of Interface and Abstract Class

interface Interface{
    int t = 100;
    public abstract void show();
}


abstract class Abstract{

   public Abstract(){
      System.out.println("Constructor - Abstract Class ");
   }
   public abstract void print(); 

}


public class Test extends Abstract implements Interface{

   public static void main(String args[])
   {
      Test obj = new Test();
      obj.show();
      obj.print();
   }
   
   @Override
   public void show(){
       System.out.println("Show()");
   }

   @Override
   public void print(){
       System.out.println("Print()");
   }

}