Java extends example

Question

i have a java beginner question: Parent.print() prints "hallo" in the console, but also Child.print() prints "hallo". I thought it has to print "child". How can i solve this?

public class Parent {

    private String output = "hallo";

    public void print() {
        System.out.println(output);
    }

}

public class Child extends Parent {

   private String output = "child";

}

Answer 1

Currently you've got two separate variables, and the code in Parent only knows about Parent.output. You need to set the value of Parent.output to "child". For example:

public class Parent {

  private String output = "hallo";

  protected void setOutput(String output) {
    this.output = output;
  }

  public void print() {
    System.out.println(output );
  }
}

public class Child extends Parent {
  public Child() {
    setOutput("child");
  }
}

An alternative approach would be to give the Parent class a constructor which took the desired output:

public class Parent {
  private String output;

  public Parent(String output) {
    this.output = output;
  }

  public Parent() {
    this("hallo");
  }

  public void print() {
    System.out.println(output );
  }
}

public class Child extends Parent {
  public Child() {
    super("child");
  }
}

It really depends on what you want to do.