Question

1. Can you extend an abstract class? In what situation can you not inherit/extend a class?

2. Can you still make it an abstract class if a class does not have any abstract methods?

Answer 1

First of all, let's understand the meaning of Abstract class.

Abstract class:

• An abstract class is a class that is declared abstract.
• It may or may not include abstract methods.
• It cannot be instantiated, but they can be subclassed.

Answer - Question: 1

Yes, we can extend an abstract class.

abstract class Animal{
   public abstract void sound();
}


public class Dog extends Animal{

   public void sound(){
        System.out.println("Woof");
   }
}

• Any class inheriting the current class must either override the abstract method or declare itself as abstract.
• So, if we are not overriding, we can't inherit/extend.

Answer - Question: 2

• Yes, we can have an abstract class without Abstract Methods as both are independent concepts.
• Declaring a class abstract means that it can not be instantiated on its own.
• Declaring a method abstract means that Method will be defined in the subclass.

public abstract class AbstractClass{

    public String nonAbstractMethod1(int a, int b){
        int c = a + b;
        return c;
    }

    public static void nonAbstractMethod2(int c){
        System.out.println("Value of c is "+ c);
    }
}

Please let me know in the comments in case of any confusion. Also, please upvote if you like.