MCQ on Inheritance in java: Top 30

MCQ 1: What does the `super` keyword do in Java? 

   – a) Invokes parent class constructor 

   – b) Invokes child class constructor 

   – c) Calls a static method 

   – d) Accesses instance variables of child class 

   Correct Answer: a) Invokes parent class constructor 

   Explanation: The `super` keyword in Java is used to invoke the parent class constructor. It is typically used within the constructor of a subclass to call the constructor of its superclass. 

 MCQ 2: When is the `super` keyword used to invoke a method in Java? 

   – a) When the method is declared as private in the superclass 

   – b) When the method is overridden in the subclass 

   – c) When the method is declared as static in the superclass 

   – d) When the method is declared as final in the superclass 

   Correct Answer: b) When the method is overridden in the subclass 

   Explanation: The `super` keyword is used to invoke the parent class method when the method is overridden in the subclass. It ensures that the method of the parent class is executed. 

MCQ 3: What is the output of the following code snippet? 

   class Animal { 

       void eat() { System.out.println(“eating…”); } 

   } 

   class Dog extends Animal { 

       void eat() { System.out.println(“eating bread…”); } 

       void bark() { System.out.println(“barking…”); } 

       void work() { 

           super.eat(); 

           bark(); 

       } 

   } 

   class TestSuper2 { 

       public static void main(String args[]) { 

           Dog d = new Dog(); 

           d.work(); 

       } 

   } 

   – a) eating… 

   – b) eating bread… 

   – c) eating… barking… 

   – d) Compile-time error 

   Correct Answer: c) eating… barking… 

   Explanation: The `work()` method of the `Dog` class first invokes the `eat()` method of the parent class using `super.eat()`, and then it calls the `bark()` method. Therefore, the output is “eating… barking…”. 

 MCQ 4: What is the purpose of declaring a method as `final` in Java? 

   – a) To prevent the method from being overridden in subclasses 

   – b) To prevent the method from being accessed outside its class 

   – c) To allow the method to be accessed by any subclass 

   – d) To allow the method to be overridden in subclasses 

   Correct Answer: a) To prevent the method from being overridden in subclasses 

   Explanation: Declaring a method as `final` in Java prevents subclasses from overriding that method. It ensures that the behavior of the method remains constant across all subclasses. 

 MCQ 5: What happens if an attempt is made to override a `final` method in a subclass? 

   – a) Compilation error 

   – b) Runtime error 

   – c) Method in the subclass takes precedence 

   – d) Method in the superclass takes precedence 

   Correct Answer: a) Compilation error 

   Explanation: If an attempt is made to override a `final` method in a subclass, it results in a compilation error. Java does not allow the overriding of `final` methods. 

MCQ 6: What is the output of the following code snippet? 

   class Animal { 

       Animal() { System.out.println(“animal is created”); } 

   } 

   class Dog extends Animal { 

       Dog() { 

           super(); 

           System.out.println(“dog is created”); 

       } 

   } 

   class TestSuper3 { 

       public static void main(String args[]) { 

           Dog d = new Dog(); 

       } 

   } 

   “` 

   – a) animal is created dog is created 

   – b) dog is created animal is created 

   – c) animal is created 

   – d) dog is created 

   Correct Answer: a) animal is created dog is created 

   Explanation: The constructor of the `Animal` class is invoked first due to `super()` in the `Dog` class constructor, followed by the constructor of the `Dog` class. Therefore, the output is “animal is created dog is created”. 

MCQ 7: What is the purpose of the `final` keyword when applied to a variable in Java? 

   – a) It allows the variable to be accessed only within its class 

   – b) It makes the variable immutable 

   – c) It allows the variable to be reassigned multiple times 

   – d) It restricts the variable from being declared as static 

   Correct Answer: b) It makes the variable immutable 

   Explanation: When a variable is declared as `final` in Java, its value cannot be changed once assigned. It effectively makes the variable immutable. 

 MCQ 8: Which of the following statements about `final` variables in Java is true? 

   – a) They must be initialized at the time of declaration 

   – b) They can be reassigned multiple times after initialization 

   – c) They cannot be declared as instance variables 

   – d) They are automatically initialized to null if not assigned a value 

   Correct Answer: a) They must be initialized at the time of declaration 

   Explanation: `final` variables in Java must be initialized at the time of declaration. Failure to initialize them results in a compilation error. 

MCQ 9: What is the significance of a `final` class in Java? 

   – a) It cannot be instantiated 

   – b) It cannot have any methods 

   – c) It allows subclasses to override its methods 

   – d) It can be extended by any other class 

   Correct Answer: a) It cannot be instantiated 

   Explanation: When a class is declared as `final` in Java, it cannot be subclassed or extended. Additionally, it cannot be instantiated directly. 

. MCQ 10: Can a `final` method in a superclass be inherited by its subclasses in Java? 

    – a) Yes, and it can be overridden 

    – b) No, `final` methods cannot be inherited 

    – c) Yes, but it cannot be invoked 

    – d) No, `final` methods cannot be inherited or overridden 

    Correct Answer: a) Yes, and it can be overridden 

    Explanation: `final` methods in a superclass are inherited by its subclasses, but they cannot be overridden. However, the subclasses can still access and use the `final` method. 

MCQ 11: What happens if an attempt is made to declare a `final` constructor in Java? 

    – a) Compilation error 

    – b) Runtime error 

    – c) Constructor is automatically made `static` 

    – d) Constructor cannot be called from outside its class 

    Correct Answer: a) Compilation error 

    Explanation: Constructors cannot be declared as `final` in Java. Attempting to do so will result in a compilation error. 

 MCQ 12: What is a blank or uninitialized `final` variable in Java? 

    – a) A variable declared without any value assignment 

    – b) A variable declared as `final` within a method 

    – c) A variable that is declared `static` within a class 

    – d) A variable that is declared `final` within a loop 

    Correct Answer: a) A variable declared without any value assignment 

    Explanation: A blank or uninitialized `final` variable in Java is a variable declared with the `final` keyword but not assigned a value at the time of declaration. 

 MCQ 13: How can a blank `final` variable be initialized in Java? 

    – a) It can only be initialized within a method 

    – b) It can only be initialized within a loop 

    – c) It can only be initialized within a static block 

    – d) It can only be initialized within a constructor 

    Correct Answer: d) It can only be initialized within a constructor 

    Explanation: A blank `final` variable can only be initialized within a constructor in Java. Once initialized, its value cannot be changed. 

 MCQ 14: What is the significance of a static blank `final` variable in Java? 

    – a) It can be initialized multiple times 

    – b) It can only be accessed by static methods 

    – c) It must be initialized within a non-static block 

    – d) It can be initialized only within a static block 

    Correct Answer: d) It can be initialized only within a static block 

    Explanation: A static blank `final` variable in Java must be initialized within a static block. Once initialized, its value remains constant throughout the program’s execution. 

. MCQ 15: What is the purpose of declaring a parameter as `final` in a method in Java? 

    – a) It restricts the parameter from being accessed within the method 

    – b) It allows the parameter to be modified within the method 

    – c) It prevents the parameter from being reassigned within the method 

    – d) It prevents the parameter from being passed to the method 

    Correct Answer: c) It prevents the parameter from being reassigned within the method 

    Explanation: Declaring a parameter as `final` in a method in Java prevents its value from being changed or reassigned within the method. It ensures the parameter remains constant. 

16. MCQ 16: Is it possible to declare a constructor as `final` in Java? 

    – a) Yes, and it prevents the class from being instantiated 

    – b) No, constructors cannot be declared as `final` 

    – c) Yes, and it ensures that the constructor cannot be inherited 

    – d) No, constructors are always `final` by default 

    Correct Answer: b) No, constructors cannot be declared as `final` 

    Explanation: Constructors in Java cannot be declared as `final`. They are always implicitly `final` and cannot be overridden. 

MCQ 17: What is the output of the following code snippet? 

    class Bike11 { 

        int cube(final int n) { 

            n = n + 2; 

            n n n; 

        } 

        public static void main(String args[]) { 

            Bike11 b = new Bike11(); 

            b.cube(5); 

        } 

    } 

    “` 

    – a) Compilation error 

    – b) Runtime error 

    – c) Output: 125 

    – d) Output: Compile Time Error 

    Correct Answer: d) Output: Compile Time Error 

    Explanation: The code snippet attempts to modify the value of a `final` parameter `n` within the `cube()` method, which results in a compilation error. 

MCQ 18: What happens if an attempt is made to inherit from a `final` class in Java? 

    – a) Compilation error 

    – b) Runtime error 

    – c) Class inherits normally 

    – d) Class inherits but cannot access any methods 

    Correct Answer: a) Compilation error 

    Explanation: Attempting to inherit from a `final` class in Java results in a compilation error. `final` classes cannot be subclassed. 

MCQ 19: What is the primary purpose of the `final` keyword in Java? 

    – a) To improve performance 

    – b) To enforce encapsulation 

    – c) To restrict subclassing, method overriding, or variable reassignment 

    – d) To enable multithreading 

    Correct Answer: c) To restrict subclassing, method overriding, or variable reassignment 

    Explanation: The primary purpose of the `final` keyword in Java is to restrict certain behaviors such as subclassing, method overriding, or variable reassignment. 

MCQ 20: Can a `final` method be overloaded in Java? 

    – a) Yes, but it cannot be overridden 

    – b) Yes, and it can be overridden 

    – c) No, `final` methods cannot be overloaded 

    – d) No, `final` methods cannot be inherited 

    Correct Answer: a) Yes, but it cannot be overridden 

    Explanation: `final` methods can be overloaded in Java, meaning multiple methods with the same name but different parameters can exist in the same class. However, they cannot be overridden by subclasses. 

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