Override private method

Question

I am reading "Thinking in Java" and have a doubt. In the chapter "reusing classes", section "final and private", it says that a private method cannot be overridden. However, I tried it on the machine. It actually could be overridden.

Here is the code:

class Amphibian {
     private void print() { System.out.println("in Amphibian"); }
}

public class Frog extends Amphibian {
     public void print() { System.out.println("in Frog"); }

     public static void main(String[] args) {
          Frog f = new Frog();
          f.print();
     }
}

That prints:

in Frog

Answer 1

You didn't override it, you just hid it with a new method with the same name.

If you didn't create a new print() method, your Frog class wouldn't have one.

Answer 2

To illustrate the difference between overriding and hiding, consider this:

class Amphibian {
    private void print() { System.out.println("in Amphibian"); }
    public void callPrint() {
        /* 
         * This will DIRECTLY call Amphibian.print(), regardless of whether the
         * current object is an instance of Amphibian or Frog, and whether the
         * latter hides the method or not.
         */
        print(); // this call is bound early
    }
}

class Frog extends Amphibian {
    public void print() { System.out.println("in Frog"); }
    public static void main(String[] args) {
        Frog f = new Frog();
        f.callPrint(); // => in Amphibian

        // this call is bound late
        f.print(); // => in Frog
    }
}

The "overriding" (i.e. hiding) method doesn't get called, the one in the parent class does. Which means it's not really an override.