25 Unique MCQ Question on Classes and Objects

 25 Unique MCQ Question on Classes and Objects 

1.  Which keyword is used to prevent inheritance of a class in Java? 

   a.  sealed   

   b.  final   

   c.  private   

   d.  restrict 

2.  In Java, what is the purpose of the  toString()  method? 

   a. Converts an object to an integer  

   b. Converts an object to a string representation  

   c. Defines a new class  

   d. Deletes the object

3.  What is the purpose of the 'super' keyword in Java when referring to a method or variable? 

   a. Calls the superclass method or variable  

   b. Calls the current class method or variable  

   c. Calls a static method  

   d. Refers to the current object

4.  In Java, which access modifier is stricter than 'private'? 

   a.  protected   

   b.  package-private   

   c.  public   

   d.  static 

5.  How is a constant variable defined in a Java class? 

   a. Using the  const  keyword  

   b. By declaring it inside a method  

   c. Using  final  keyword and uppercase letters with underscores  

   d. Constants are not allowed in Java classes

6.  Which keyword is used to declare an interface in Java? 

   a.  interface   

   b.  implements   

   c.  class   

   d.  extends 

7.  In Java, what is the purpose of the  static  keyword in a method or variable? 

   a. It allows access only within the same class  

   b. It can be called without creating an instance of the class  

   c. It is used for method overloading  

   d. It prevents inheritance

8.  What is the significance of the 'this' keyword in Java? 

   a. Refers to the current instance of the class  

   b. Refers to the superclass  

   c. Represents a global variable  

   d. Defines a new object

9.  In Java, what is the purpose of the  @Override  annotation? 

   a. Marks a method as static  

   b. Overrides a method from the superclass  

   c. Implements a new method  

   d. Denotes a constant variable

10.  What does the term 'encapsulation' refer to in Java? 

    a. Combining different data types  

    b. Hiding the implementation details  

    c. Storing data in a class  

    d. Allowing access to all class members

11.  Which type of inheritance involves a class inheriting from more than one class in Java? 

    a. Single Inheritance  

    b. Multiple Inheritance  

    c. Hierarchical Inheritance  

    d. Multilevel Inheritance

12.  What is the role of the 'instanceof' operator in Java? 

    a. Checks if two objects are the same  

    b. Compares the values of two objects  

    c. Checks if an object is an instance of a class  

    d. Checks for class inheritance

13.  In Java, what is the purpose of the  final  keyword when applied to a class? 

    a. It prevents the instantiation of the class  

    b. It allows the class to be inherited  

    c. It marks a class as abstract  

    d. It denotes a constant variable

14.  What is the purpose of the 'enum' keyword in Java? 

    a. It defines an interface  

    b. It declares a constant variable  

    c. It represents an enumeration of values  

    d. It denotes an abstract class

15.  In Java, what is the purpose of the  throws  keyword in a method signature? 

    a. It declares checked exceptions that a method might throw  

    b. It specifies the return type of the method  

    c. It indicates that the method is abstract  

    d. It denotes a static method

16.  What is the role of the 'abstract' keyword in Java? 

    a. Marks a method as final  

    b. Allows instantiation of the class  

    c. Denotes a constant variable  

    d. Declares an abstract class or method

17.  Which keyword is used to create an object of a class in Java? 

    a.  create   

    b.  new   

    c.  instantiate   

    d.  object 

18.  In Java, what is the purpose of the  instanceof  operator? 

    a. Checks if two objects are the same  

    b. Compares the values of two objects  

    c. Checks if an object is an instance of a class  

    d. Checks for class inheritance

19.  Which of the following is a valid way to call a superclass method in Java? 

    a.  super.method()   

    b.  this.method()   

    c.  Subclass.method()   

    d.  parent.method() 

20.  What is the purpose of the  default  keyword in Java interfaces? 

    a. It defines a default implementation of a method  

    b. It specifies a default value for a variable  

    c. It marks a method as non-accessible  

    d. It denotes an abstract method

21.  In Java, what does the  protected  access modifier allow? 

    a. Access within the same class only  

    b. Access within the same package and its subclasses  

    c. Access from any class  

    d. No access is allowed

22.  Which of the following statements is true regarding the 'try-catch' block in Java? 

    a. It must be used for all methods  

    b. It is used to handle checked exceptions  

    c. It is optional and can be omitted  

    d. It is only used for loops

23.  What is the purpose of the 'transient' keyword in Java? 

    a. It marks a variable as non-transient  

    b. It prevents serialization of a variable  

    c. It allows serialization of a variable  

    d. It denotes a constant variable

24.  In Java, what is the purpose of the  interface  keyword? 

    a. It defines a class  

    b. It declares an interface  

    c. It represents an enumeration of values  

    d. It declares a constant variable

25.  Which of the following is true regarding the 'this' keyword in Java? 

    a. Refers to the current instance of the class  

    b. Refers to the superclass  

    c. Represents a global variable  

    d. It is used to create a new instance of the class

1. b. 

2. b. 

3. a. 

4. a. 

5. c. 

6. b. 

7. b. 

8. a. 

9. b. 

10. b.

11. b.

12. c.

13. a.

14. c. 

15. a. 

16. d. 

17. b. 

18. c. 

19. a. 

20. a. 

21. b. 

22. b. 

23. b. 

24. b. 

25. a.