How can you create an abstract class in Java with a constructor and abstract and non-abstract methods? Can you provide an example of a subclass that inherits the abstract class and implements the abstract method?

Meta Description: Learn how to create an abstract class with a constructor and abstract and non-abstract methods in Java. See an example of a subclass that inherits the abstract class and implements the abstract method.

The implementation of the code:

Source code:

abstract class AbstractClass {

    public AbstractClass() {

        System.out.println("This is constructor of abstract class");

    }

    public abstract void a_method();

    public void normal_method() {

        System.out.println("This is a normal method of abstract class");

    }

}

class SubClass extends AbstractClass {

    public void a_method() {

        System.out.println("This is abstract method");

    }

}

 

public class Main {

    public static void main(String[] args) {

        SubClass obj = new SubClass();

        obj.a_method();

        obj.normal_method();

    }

} 

In this code, we have defined an abstract class AbstractClass with a constructor that prints "This is constructor of abstract class", an abstract method a_method, and a non-abstract method normal_method that prints "This is a normal method of abstract class".

 

We have also defined a concrete class SubClass that extends the AbstractClass and provides the implementation for the abstract method a_method.

 

Finally, we create an object obj of the SubClass class and call the a_method and normal_method methods of the AbstractClass using the obj reference. When we run the program,

we get the following output:

This is constructor of abstract class

This is abstract method

This is a normal method of abstract class

As we can see from the output, the constructor of the AbstractClass is called when we create an object of the SubClass because it is the superclass of SubClass. After that, we call the a_method method of the SubClass, which overrides the a_method method of the AbstractClass and prints "This is abstract method" to the console. 

Finally, we call the normal_method method of the AbstractClass, which is inherited by the SubClass, and prints "This is a normal method of abstract class" to the console.