Overriding Methods

We need a new show() method in the class Movie:

// added to class Movie
public void show()
{
  System.out.println( title + ", " + length + " min. available:" + avail );
  System.out.println( "dir: " + director + "  " + rating );  
}

Now, even though the parent has a show() method the new definition of show() in the child class will override the parent's version.

A child's method overrides a parent's method when it has the same signature as a parent method. Now the parent has its method, and the child has its own method with the same signature. (Remember that the signature of a method is the name of the method and its parameter list.)

An object of the parent type will include the method given in the parent's definition. An an object of the child type will include the method given in the child's definition.

With the change in the class Movie the following program will print out the full information for both items.

class TapeStore
{
  public static void main ( String args[] )
  {
    VideoTape item1 = new VideoTape("Microcosmos", 90 );
    Movie     item2 = new Movie("Jaws", 120, "Spielberg", "PG" );
    item1.show();
    item2.show();
  }
}

The line item1.show() calls the show() method defined in VideoTape, and the line item2.show() calls the show() method defined in Movie.

Microcosmos, 90 min. available:true
Jaws, 120 min. available:true
dir: Spielberg PG