AnimalTest.java Answers

// ANSWERS:
//
// (1) Write the class Cow which extends class Animal.  Override all
// necessary methods.
//
// HINT: Look at how class Dog inherits from class Animal and
// follow the pattern.
// 

class Cow extends Animal
{
   public void talk()
   {
      System.out.println("Moo!");
   }
}

// 
// (2) Write the class Bird which extends class Animal.  Override all
// necessary methods.
//

class Bird extends Animal
{
   public boolean hasWings()
   {
      return true;
   }
   public boolean canFly()
   {
      return true;
   }
   public void talk()
   {
      System.out.println("Tweet tweet!");
   }
}

// 
// (3) Write the class Kiwi which extends class Bird.  Override all
// necessary methods.
// 

class Kiwi extends Bird {
   public boolean canFly() {
      return false;
   }
   public void talk() {
      System.out.println("Kiiiii-wiiii!");
   }
}

// 
// (4) Run the AnimalTest class to make sure that all the methods
// work correctly.
//
// (5) Rewrite the chatter method so that it never calls the
// talk methods and instead uses a series of "if" statements
// and the "instanceof" operator to test the run-time type
// of each object in the array "a".
// 

public void chatter(Animal[] a) {
   // Note that the subclasses must appear
   // before superclasses in the following
   // list, otherwise the wrong message will
   // be printed out for subclasses.
   for (int i=0; i<a.length; i++) {
      if (a[i] instanceof Kiwi) {
         System.out.println("Kiiiii-wiiii!");
      }
      else if (a[i] instanceof Bird) {
         System.out.println("Tweet tweet!");
      }
      else if (a[i] instanceof Dog) {
         System.out.println("Woof woof");
      }
      else if (a[i] instanceof Cow) {
         System.out.println("Moo!");
      }
      else {
         /* it must be an Animal */
      }
   }
}

//