377: Mainline

Occasionally, you need to work with predicates that work on class instances, rather than on numbers. For example, if you want to determine whether a particular instance is an instance of a particular class, you use the instanceof operator, which returns true if the instance is either a direct instance of the given class or a direct instance of a subclass of that class.

Suppose, for example, that the JamesBondMovie class extends the Movie class, which extends the Attraction class. Then, a James Bond movie is an instance of all three classes. An ordinary movie is an instance of the Movie class as well as of the Attraction class, but it is not an instance of the JamesBondMovie class:

public class Demonstrate { 
 public static void main (String argv[]) { 
  JamesBondMovie jbm = new JamesBondMovie(); 
  Movie m = new Movie(1, 1, 1); 
  System.out.println(jbm instanceof Attraction); 
  System.out.println(jbm instanceof Movie); 
  System.out.println(jbm instanceof JamesBondMovie); 
  System.out.println(m instanceof Attraction); 
  System.out.println(m instanceof Movie); 
  System.out.println(m instanceof JamesBondMovie); 
 } 
} 
--- Result --- 
true 
true 
true 
true 
true 
false