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javasubclassextendssuperclasssuper

Wondering about the output of the following Java program

I am dealing with some past exam papers and here I am not sure of the output. I think I am not clear about extends and super.

public class Superclass{
    public boolean aVariable;

    public void aMethod(){
        aVariable = true;
    }
}

class Subclass extends Superclass {
    public boolean aVariable;

    public void aMethod() {
      aVariable = false;
      super.aMethod();
      System.out.println(aVariable);
      System.out.println(super.aVariable);
    }
}

I think that the second output would be true since it would refer to the super class and it is an object. However, I am not sure of the first output. Would it be just a value and print false or it is also an object?

Solution

  • The output will be:

    false
true

    Because in your Subclass aVariable is false by default (so assignation aVariable = false; is needless). Read more about Primitive Data Types default values.
    And in Superclass you initialize aVariable as true by invoking the superclass' method using the keyword super: super.aMethod();. Read more about Accessing Superclass Members.

    Take a look on demo.