abstract public class Animal { abstract public void greeting(); } public class C

Question

abstract public class Animal {
  abstract public void greeting();
}

public class Cat extends Animal {
  @Override
  public void greeting() {
     System.out.println("Meow!");
  }
}

public class Dog extends Animal {
  @Override
  public void greeting() {
     System.out.println("Woof!");
  }
  
  public void greeting(Dog another) {
     System.out.println("Woooooooooof!");
  }
}

public class BigDog extends Dog {
  @Override
  public void greeting() {
     System.out.println("Woow!");
  }
  
  @Override
  public void greeting(Dog another) {
     System.out.println("Woooooowwwww!");
  }
}

Explain the outputs (or error) for the following test program. Make sure to include what line th error is on, a discription, and if it is an output error or error. List all lines, the code is supposed to have errors, which you will be finding and describing.

1 public class TestAnimal {
2   public static void main(String[] args) {
3      // Using the subclasses
4      Cat cat1 = new Cat();
5      cat1.greeting();
6      Dog dog1 = new Dog();
7      dog1.greeting();
8      BigDog bigDog1 = new BigDog();
9      bigDog1.greeting();
10       
11      // Using Polymorphism
12      Animal animal1 = new Cat();
13      animal1.greeting();
14      Animal animal2 = new Dog();
15      animal2.greeting();
16      Animal animal3 = new BigDog();
17      animal3.greeting();
18      Animal animal4 = new Animal();
19      
20      // Downcast
21      Dog dog2 = (Dog)animal2;
22      BigDog bigDog2 = (BigDog)animal3;
23      Dog dog3 = (Dog)animal3;
24      Cat cat2 = (Cat)animal2;
25      dog3.greeting(dog2);
26      dog2.greeting(bigDog2);
27      bigDog2.greeting(dog2);
28   }
29 }

Explanation / Answer

There are two errors in the code of TestAnimal Class and remaining classes are error free. I added the explanation above the line of error.

public class TestAnimal {
public static void main(String[] args) {
// Using the subclasses
Cat cat1 = new Cat();
cat1.greeting();
Dog dog1 = new Dog();
dog1.greeting();
BigDog bigDog1 = new BigDog();
bigDog1.greeting();
// Using Polymorphism
Animal animal1 = new Cat();
animal1.greeting();
Animal animal2 = new Dog();
animal2.greeting();
Animal animal3 = new BigDog();
animal3.greeting();
// As the Animal class is abstract you cannot instantiate the object
Animal animal4 = new Animal();
  
// Downcast
Dog dog2 = (Dog)animal2;
BigDog bigDog2 = (BigDog)animal3;
Dog dog3 = (Dog)animal3;
// You cannot cast a parent class to children. The reverse is possible
Cat cat2 = (Cat)animal2;
dog3.greeting(dog2);
dog2.greeting(bigDog2);
bigDog2.greeting(dog2);
}
}

**Comment for any further queries.

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