this is Java

How come our method showPrice works with CompactDisc and DvdMovie objects? What can you say about the RetailItem class just by looking at this code fragment?

public class PolymorphicInterfaceDemo{ public static void main(String[] args) { CompactDisc cd = new CompactDisc("Greatest Hits", "Joe Looney Band", 18.95); DvdMovie movie = new DvdMovie("Wheels of Fury", 137, 12.95);

System.out.println("Item #1: " + cd.getTitle()); showPrice(cd); System.out.println("Item #2: " + movie.getTitle()); showPrice(movie); }

private static void showPrice(RetailItem item) { System.out.printf("Price: $%,.2f ", item.getRetailPrice());

} }