Unit4

Question 1

1. What is the primary purpose of inheritance in object-oriented programming?
   
   • a) To allow new objects to be made from existing ones.
   • b) To allow classes to derive from multiple base classes.
   • c) To provide a way for classes to obtain all the properties and behaviors of another class.
   • d) To restrict access to methods in the superclass.

Answer 1

Correct Answer: c) To provide a way for classes to obtain all the properties and behaviors of another class.

Question 2

2. Which statement is true about polymorphism?
   
   • a) It allows methods to perform differently in different instances.
   • b) It restricts methods from being overridden.
   • c) It only applies to static methods.
   • d) It prevents classes from inheriting features from their parent classes.

Answer 2

Correct Answer: a) It allows methods to perform differently in different instances.

Question 3

3. What does the extends keyword signify in a Java class definition?
   
   • a) The class is being enhanced with additional methods.
   • b) The class is providing new implementations for base class methods.
   • c) The class is inheriting from a superclass.
   • d) The class cannot be instantiated.

Answer 3

Correct Answer: c) The class is inheriting from a superclass.

Question 4

*Consider the following classes:
javaCopy code
public class Fruit {
public void flavor() { System.out.println(“Fruit flavor”); }
}
public class Orange extends Fruit {
public void flavor() { System.out.println(“Orange flavor”); }
}

What is this an example of?**

• a) Overloading
• b) Overriding
• c) Dynamic Binding
• d) Static Binding

Answer 4

Correct Answer: b) Overriding

Question 5

5. Which of the following is a correct example of polymorphism?
   
   • a) Fruit myFruit = new Orange();
   • b) Orange myOrange = new Fruit();
   • c) Fruit myFruit = new Fruit();
   • d) Orange myOrange = new Orange();

Answer 5

Correct Answer: a) Fruit myFruit = new Orange();

Question 6

6. What is early binding?
   
   • a) The type of binding where method calls are resolved at runtime.
   • b) The type of binding where method calls are resolved as soon as the class is loaded.
   • c) The type of binding where method calls are resolved at compile time.
   • d) The type of binding that occurs only in interpreted languages.

Answer 6

Correct Answer: c) The type of binding where method calls are resolved at compile time.

Question 7

7. What is the result of the super keyword in an overridden method?
   
   • a) It calls the overridden method in the superclass.
   • b) It prevents the method from being overridden.
   • c) It deletes the method from the superclass.
   • d) It renames the method in the superclass.

Answer 7

Correct Answer: a) It calls the overridden method in the superclass.

Question 8

8. How does Java implement multiple inheritances?
   
   • a) Through direct extension of multiple classes.
   • b) Through interfaces.
   • c) Java does not support multiple inheritances.
   • d) Through virtual classes.

Answer 8

Correct Answer: b) Through interfaces. (Note: Java does not support multiple inheritances through classes but allows a class to implement multiple interfaces.)

Question 9

9. Which of these is a use of downcasting?
   
   • a) To access methods that the reference type doesn’t have.
   • b) To restrict the functionality of an object.
   • c) To convert primitive types into objects.
   • d) To prevent exceptions in method calls.

Answer 9

Correct Answer: a) To access methods that the reference type doesn’t have.

Question 10

10. What is displayed when a subclass object calls super.methodName() and this method is overridden in the subclass?
    
    • a) The method in the superclass is called.
    • b) The method in the subclass is called.
    • c) A runtime error occurs.
    • d) A compile-time error occurs.

Answer 10

Correct Answer: a) The method in the superclass is called.