Java Questions 28

1. When does the instance of operator return true?
   Answer:
   The instanceof operator returns true if the reference variable being tested is of the type being compared to.
2. What is true of every class in Java?
   Answer:
   Every class in Java is a subclass of class Object (except of course the class Object).
3. What is true about every class that you create?
   Answer:
   Whenever you create a class, you automatically inherit all of the methods in the class Object.
4. What are the two most common reasons to use inheritance?
   Answer:
   The 2 most common reasons to use inheritance are
   1. To promote code resuse
   2. To use polymorphism.


5. The IS-A relationships is based on ?
   Answer:
   The concept of IS-A is based on
   1. class inheritance or
   2. interface implementation
6. Give two examples of a "IS-A Relationship"?
   Answer:
   A mustang "is a" type of horse.
   A grizzly "is a" type of bear.
7. Answer:
   Animal is a superclass of mammal.
   Mammal is a superclass of human.
8. How does the "IS-A" relationship relate to the extends keyword?
   Answer:
   Car extends Vehicle means Car "IS-A" vehicle.
9. Write a class Mammal that inherits from Animal.
   public class Animal{}
   Answer:
   

   public class Mammal extends Animal{
   	private Lungs mammalLungs;
   }
   

10. What test must a Java object pass in order to be considered polymorphic?
    Answer:
    Any Java object that can pass more than one IS-A test can be considered polymorphic.