Reference Variable Casting

[Nelo Angelo]

This block of code is given in SCJP Sun Certified Programmer for Java 6 Exam - Mc Graw Hill.

I am not able to understand what some of the lines actually does.

class Animal
{
    void makeNoise() {System.out.println(bark); }
}

class Dog extends Animal
{
    void makeNoise() {System.out.println("bark"); }
    void playDead() {System.out.println("roll over"); }
}

class CastTest2
{
   public static void main(String args[])
   {
        Animal [] a= {new Animal(), new Dog(), new Animal() };    //Why are they using two animal objects?
        
        for(Animal animal: a)   //What does this line do?
        {
             animal.makeNoise();
             if (animal instanceof Dog)
              {
                        Dog d=(Dog) animal;
                        d.playDead(); 
               }
        }
   }
}

[Zachary Pepin]

As for your first question, I'm not sure why they created two Animal objects.

As for the loop, basically, it is meant to be a simpler syntax for iterating over a set of objects. You can think of the colon as being like the word "in", so it is saying something like "for each Animal in a, do this". For an array like this, it is shorter than writing something like the following.

for (int i = 0; i < a.length; i++) {
    Animal animal = a[i];

    ...
}

[Jesper de Jong]

See: The For-Each Loop. This was a new feature of Java 5.

[Nelo Angelo]

@Zachary n @Jesper
Thanks a lot

@Zachary
Very nicely illustrated.