Java OCA OCP Practice Question 1321

Question

Given the class definitions below, which value, when inserted into the blank line, does not allow the class to compile? 

public class Animal {} 

public class Dog extends Animal {} 

public class Wolf extends Animal {} 

public final class Husky extends Dog {} 

public class Main { 
   Animal animal; //from w  w  w. j  a  va2 s .c o  m
   public final void setAnimal(Dog animal) { this.animal = animal; } 
   public static void main(String[] furryFriends) { 
      new Main().setAnimal( ___ ); 
   } 
}
  • A. new Husky()
  • B. new Dog()
  • C. new Wolf()
  • D. null 


C.

Note

The setAnimal() method requires an object that is Dog or a subclass of Dog.

Since Husky extends Dog, Options A and B both allow the code to compile.

Option D is also valid because a null value does not have a type and can be assigned to any reference variable.

Option C is the only value that prevents the code from compiling because Wolf is not a subclass of Dog.

Even though Wolf can be assigned to the instance Animal variable, the setter requires a compatible parameter.




PreviousNext

Related