Advanced Object-Oriented Programming Practice Quiz

Advanced Object-Oriented Programming Practice Quiz

 

1. Which of the following is a core concept of Object-Oriented Programming (OOP)?

• A) Procedures
• B) Encapsulation
• C) Arrays
• D) Conditional Statements
  Answer: B) Encapsulation

2. What does inheritance allow in OOP?

• A) Code duplication
• B) Reusability of code
• C) Data hiding
• D) Function overloading
  Answer: B) Reusability of code

3. Which of the following is NOT a type of polymorphism in OOP?

• A) Compile-time polymorphism
• B) Runtime polymorphism
• C) Data polymorphism
• D) Method overloading
  Answer: C) Data polymorphism

4. In OOP, what is encapsulation primarily used for?

• A) Improving performance
• B) Hiding the internal state of an object
• C) Reusing code
• D) Supporting multiple inheritance
  Answer: B) Hiding the internal state of an object

5. Which of the following keywords is used to declare an abstract class in Java?

• A) abstract
• B) interface
• C) class
• D) void
  Answer: A) abstract

6. What is the main difference between a class and an interface in Java?

• A) A class can have methods with implementation, while an interface can only have method declarations.
• B) A class can only inherit from one class, while an interface can inherit from multiple interfaces.
• C) A class cannot have fields, but an interface can.
• D) There is no difference; they are the same in Java.
  Answer: A) A class can have methods with implementation, while an interface can only have method declarations.

7. Which of the following best describes the concept of polymorphism in OOP?

• A) An object can assume many forms.
• B) An object can inherit from multiple classes.
• C) A class can contain multiple constructors.
• D) An object’s state is hidden.
  Answer: A) An object can assume many forms.

8. In OOP, what does the “this” keyword refer to?

• A) The current class
• B) The current object
• C) A reference variable
• D) The superclass
  Answer: B) The current object

9. What is the purpose of a constructor in OOP?

• A) To initialize the object
• B) To destroy the object
• C) To define methods
• D) To handle exceptions
  Answer: A) To initialize the object

10. Which of the following is true about a static method in Java?

• A) It can access instance variables of the class.
• B) It can be called without creating an instance of the class.
• C) It requires an instance to be invoked.
• D) It cannot be overridden.
  Answer: B) It can be called without creating an instance of the class.

11. What does method overloading mean in OOP?

• A) Methods with the same name and different return types
• B) Methods with the same name and different parameters
• C) Methods with the same name and the same parameters
• D) Methods with different names and the same parameters
  Answer: B) Methods with the same name and different parameters

12. Which access modifier allows a member to be accessible only within its own package?

• A) public
• B) private
• C) protected
• D) default
  Answer: D) default

13. Which of the following statements about inheritance is correct?

• A) A subclass can access all private members of its superclass.
• B) A subclass can only access public members of its superclass.
• C) Inheritance does not allow access to the superclass’s members.
• D) A subclass can override final methods of the superclass.
  Answer: B) A subclass can only access public members of its superclass.

14. In Java, what does the term “abstract” mean for a method?

• A) The method cannot be inherited.
• B) The method does not have a body and must be implemented by subclasses.
• C) The method has no parameters.
• D) The method is private and cannot be overridden.
  Answer: B) The method does not have a body and must be implemented by subclasses.

15. What is the purpose of the “super” keyword in Java?

• A) To call the constructor of the current class
• B) To call the constructor of the superclass
• C) To define a superclass
• D) To create a new instance of a class
  Answer: B) To call the constructor of the superclass

16. Which of the following is a feature of an abstract class?

• A) It can have both abstract and non-abstract methods.
• B) It cannot have fields.
• C) It can only inherit from interfaces.
• D) It cannot be extended by other classes.
  Answer: A) It can have both abstract and non-abstract methods.

17. What is the main advantage of using interfaces in Java?

• A) They provide a mechanism for method overloading.
• B) They allow multiple inheritance of behavior.
• C) They can provide default implementations of methods.
• D) They reduce memory usage.
  Answer: B) They allow multiple inheritance of behavior.

18. In Java, which method is used to start a thread?

• A) run()
• B) execute()
• C) start()
• D) begin()
  Answer: C) start()

19. Which of the following is true for an interface?

• A) An interface can extend a class.
• B) All methods in an interface must be abstract by default.
• C) An interface can have instance variables.
• D) An interface can provide method implementations.
  Answer: B) All methods in an interface must be abstract by default.

20. Which of the following is an example of method overriding in Java?

• A) A subclass method with the same name, same parameter types, but different return type.
• B) A subclass method with the same name and the same parameter types as the superclass method.
• C) A subclass method with a different name but similar functionality.
• D) A superclass method being made static.
  Answer: B) A subclass method with the same name and the same parameter types as the superclass method.

21. What is the primary difference between a deep copy and a shallow copy in object cloning?

• A) A shallow copy creates copies of the objects, while a deep copy references the original object.
• B) A deep copy copies all the objects and their references, while a shallow copy copies only the references.
• C) A deep copy can be done only for primitive types, while a shallow copy can be done for objects.
• D) There is no difference between the two.
  Answer: B) A deep copy copies all the objects and their references, while a shallow copy copies only the references.

22. What is the purpose of the “instanceof” operator in Java?

• A) To check if an object is an instance of a class or implements an interface
• B) To instantiate a new object
• C) To create a new class
• D) To return the class type of an object
  Answer: A) To check if an object is an instance of a class or implements an interface

23. Which of the following is true about the “final” keyword in Java?

• A) A final class cannot be subclassed.
• B) A final method cannot be overridden.
• C) A final variable cannot be reassigned.
• D) All of the above
  Answer: D) All of the above

24. Which of the following is NOT an advantage of using inheritance?

• A) Code reusability
• B) Hierarchical classification
• C) Tight coupling
• D) Extending functionality
  Answer: C) Tight coupling

25. What is the result of trying to access a private member from a subclass in Java?

• A) Compile-time error
• B) The value is accessible, but cannot be modified
• C) Runtime error
• D) The value can be accessed and modified
  Answer: A) Compile-time error

26. What is the purpose of the “clone()” method in Java?

• A) To create a new object of the same class
• B) To create an exact copy of the object
• C) To copy the object’s variables only
• D) To compare two objects
  Answer: B) To create an exact copy of the object

27. What does the “static” keyword mean when used in a class method?

• A) The method is not associated with any instance of the class.
• B) The method can be called only from an instance of the class.
• C) The method must be overridden by subclasses.
• D) The method can be called without an object but requires a reference variable.
  Answer: A) The method is not associated with any instance of the class.

28. Which of the following terms refers to the ability to redefine a method in a subclass?

• A) Polymorphism
• B) Inheritance
• C) Abstraction
• D) Encapsulation
  Answer: A) Polymorphism

29. What does the “super()” keyword do?

• A) Calls the constructor of the current class
• B) Calls the constructor of the superclass
• C) Calls the constructor of the subclass
• D) Accesses the superclass methods
  Answer: B) Calls the constructor of the superclass

30. In Java, which of the following can be inherited?

• A) Variables
• B) Methods
• C) Constructors
• D) A and B only
  Answer: D) A and B only

 

31. Which of the following can be used to restrict inheritance in Java?

• A) private
• B) static
• C) final
• D) transient
  Answer: C) final

32. In Java, which of the following types of inheritance is not allowed?

• A) Single inheritance
• B) Multiple inheritance (using interfaces)
• C) Multiple inheritance (using classes)
• D) Multilevel inheritance
  Answer: C) Multiple inheritance (using classes)

33. What happens when an object is passed to a method by reference in Java?

• A) A new object is created inside the method.
• B) The original object is modified outside the method.
• C) The original object is not modified.
• D) The method does not have access to the object.
  Answer: B) The original object is modified outside the method.

34. What does the “default” keyword in an interface provide?

• A) A method with no implementation
• B) A default constructor
• C) A method with a default implementation
• D) A default value for variables
  Answer: C) A method with a default implementation

35. What is the output of calling super() in a constructor of a subclass?

• A) It will call the constructor of the superclass with no arguments.
• B) It will call the constructor of the superclass with arguments.
• C) It will cause a compilation error.
• D) It will call the constructor of the current class.
  Answer: A) It will call the constructor of the superclass with no arguments.

36. Which of the following will be the correct implementation of a singleton class in Java?

• A) Using a private constructor and a public static method
• B) Using a public constructor and a private static method
• C) Using a static constructor
• D) Using a public static instance variable only
  Answer: A) Using a private constructor and a public static method

37. Which of the following is NOT a feature of an interface in Java?

• A) It can have only abstract methods.
• B) It can have static methods.
• C) It can be implemented by multiple classes.
• D) It can have instance variables.
  Answer: D) It can have instance variables.

38. What is the role of the instanceof operator in Java?

• A) To check if a class is an instance of a subclass.
• B) To check whether an object is an instance of a specific class or implements an interface.
• C) To create a new instance of an object.
• D) To check whether a method exists in a class.
  Answer: B) To check whether an object is an instance of a specific class or implements an interface.

39. Which of the following is the correct way to call an overridden method from the superclass in Java?

• A) super.methodName();
• B) this.methodName();
• C) methodName();
• D) superCall.methodName();
  Answer: A) super.methodName();

40. In the context of Java, which of the following statements is true regarding method overriding?

• A) The method signature must be exactly the same as in the superclass.
• B) The return type can be different from the superclass.
• C) The method can have fewer parameters than in the superclass.
• D) The method must have the same name, return type, and parameters.
  Answer: A) The method signature must be exactly the same as in the superclass.

41. Which of the following methods is used to compare two objects for equality in Java?

• A) compare()
• B) equals()
• C) ==
• D) isEqual()
  Answer: B) equals()

42. Which of the following access modifiers allows a class to be visible only to classes within the same package?

• A) private
• B) public
• C) protected
• D) default
  Answer: D) default

43. What does the “volatile” keyword do in Java?

• A) Makes a variable accessible to only one thread.
• B) Ensures a variable is not cached locally in a thread.
• C) Makes a variable constant.
• D) Makes a variable inaccessible to subclasses.
  Answer: B) Ensures a variable is not cached locally in a thread.

44. What does it mean for a class to be “immutable” in Java?

• A) The class cannot be extended.
• B) The objects of the class cannot be modified after creation.
• C) The class can only have one instance.
• D) The class does not have any constructors.
  Answer: B) The objects of the class cannot be modified after creation.

45. Which of the following is the correct way to declare an abstract method in a Java interface?

• A) abstract void method();
• B) void abstract method();
• C) abstract void method() { }
• D) void method() { }
  Answer: A) abstract void method();

46. What is a “factory method” in object-oriented design?

• A) A method that instantiates an object based on some input parameters.
• B) A method used to create a new subclass.
• C) A method that factory objects with default behavior.
• D) A method used to store object instances.
  Answer: A) A method that instantiates an object based on some input parameters.

47. Which of the following best describes the principle of “composition” in OOP?

• A) An object is composed of multiple methods.
• B) An object is composed of several subclasses.
• C) An object is composed of other objects, each performing a distinct function.
• D) An object is composed of several interfaces.
  Answer: C) An object is composed of other objects, each performing a distinct function.

48. What happens if a subclass does not implement an abstract method of an interface in Java?

• A) The code will compile without any issues.
• B) The code will compile, but the method will throw an exception.
• C) The subclass will be treated as an abstract class.
• D) The code will not compile.
  Answer: D) The code will not compile.

49. Which of the following statements is true regarding a Java constructor?

• A) A constructor can return a value.
• B) A constructor must have the same name as the class.
• C) A constructor cannot be overloaded.
• D) A constructor is called only once during the class’s lifecycle.
  Answer: B) A constructor must have the same name as the class.

50. Which of the following is an example of a correct constructor chaining in Java?

• A) Calling the constructor of the subclass from the superclass.
• B) Calling one constructor of the same class from another constructor of the same class.
• C) Calling a superclass constructor from the subclass using this().
• D) Calling a superclass constructor from the subclass using super() or this().
  Answer: B) Calling one constructor of the same class from another constructor of the same class.

51. Which of the following OOP principles enables hiding the internal state of an object and only exposing necessary behavior to the outside world?

• A) Polymorphism
• B) Encapsulation
• C) Inheritance
• D) Abstraction
  Answer: B) Encapsulation

52. What is the purpose of the “final” keyword when used on a variable in Java?

• A) The variable can be assigned only once.
• B) The variable can be modified, but cannot be overridden.
• C) The variable is a constant, but can be reassigned.
• D) The variable can only be accessed by the class.
  Answer: A) The variable can be assigned only once.

53. Which of the following is the purpose of a “getter” method in OOP?

• A) To retrieve an object’s state.
• B) To initialize an object’s state.
• C) To modify an object’s state.
• D) To compare two objects for equality.
  Answer: A) To retrieve an object’s state.

54. What does the “abstract” keyword mean when used in a class definition?

• A) The class cannot be instantiated.
• B) The class can only have abstract methods.
• C) The class can only be extended by interfaces.
• D) The class must implement all abstract methods.
  Answer: A) The class cannot be instantiated.

55. Which of the following is NOT a feature of Java’s “Object” class?

• A) The toString() method.
• B) The equals() method.
• C) The hashCode() method.
• D) The clone() method.
  Answer: D) The clone() method.

56. In the context of OOP, which of the following is an example of “polymorphism”?

• A) Multiple classes sharing a single method name, but each with different implementations.
• B) A class that can inherit from multiple classes.
• C) A class using multiple constructors to instantiate objects.
• D) A class with the same name in multiple packages.
  Answer: A) Multiple classes sharing a single method name, but each with different implementations.

57. What is the purpose of the “transient” keyword in Java?

• A) It ensures that a variable is not serialized.
• B) It ensures that a variable is not assigned a value.
• C) It makes the variable volatile.
• D) It ensures that a variable is immutable.
  Answer: A) It ensures that a variable is not serialized.

58. Which of the following is true regarding the relationship between objects in composition?

• A) The composed object can exist independently of the containing object.
• B) The composed object cannot exist without the containing object.
• C) Composition creates a one-to-one relationship between objects.
• D) Composition is a form of inheritance.
  Answer: B) The composed object cannot exist without the containing object.

59. Which of the following is an example of the “open/closed principle” in OOP?

• A) Extending a class without modifying its existing code.
• B) Modifying the behavior of an existing class.
• C) Directly editing a class’s fields.
• D) Using a single class to handle all tasks.
  Answer: A) Extending a class without modifying its existing code.

60. What does “method hiding” mean in OOP?

• A) A method in a subclass with the same signature as a method in the superclass.
• B) A method in the superclass is inaccessible from the subclass.
• C) A method in the subclass is hidden from the superclass.
• D) A method is hidden because of access control modifiers.
  Answer: A) A method in a subclass with the same signature as a method in the superclass.

 

61. Which of the following best describes the concept of “polymorphism” in OOP?

• A) Multiple methods with the same name but different implementations.
• B) One method in a class.
• C) Multiple classes with identical functionality.
• D) A class that extends multiple classes.
  Answer: A) Multiple methods with the same name but different implementations.

62. What is the purpose of a “constructor” in a class?

• A) To provide a default value for an object.
• B) To initialize objects of a class.
• C) To allow an object to perform specific tasks.
• D) To create a clone of an object.
  Answer: B) To initialize objects of a class.

63. In Java, what does the term “encapsulation” refer to?

• A) Hiding internal data and exposing only necessary functionality.
• B) Reusing a method across classes.
• C) The ability to create multiple classes with the same behavior.
• D) Having multiple inheritance paths.
  Answer: A) Hiding internal data and exposing only necessary functionality.

64. Which of the following is true about interfaces in Java?

• A) An interface can have instance fields.
• B) An interface can provide implementation for its methods.
• C) A class can implement multiple interfaces.
• D) A class can extend multiple interfaces.
  Answer: C) A class can implement multiple interfaces.

65. What does the “this” keyword represent in Java?

• A) A reference to the current class.
• B) A reference to the current method.
• C) A reference to the current object.
• D) A reference to the parent class.
  Answer: C) A reference to the current object.

66. Which of the following best describes “inheritance” in OOP?

• A) The process by which one class acquires the properties and behaviors of another class.
• B) The process of hiding the internal workings of a class.
• C) The ability to create multiple versions of a method.
• D) The creation of a new class by combining two classes.
  Answer: A) The process by which one class acquires the properties and behaviors of another class.

67. In the context of Java, what does the “super” keyword do?

• A) Refers to the parent class’s constructor.
• B) Refers to the current instance of the class.
• C) Refers to the method in the current class.
• D) Refers to a sibling class.
  Answer: A) Refers to the parent class’s constructor.

68. Which of the following statements is true regarding the “final” keyword when used with a method in Java?

• A) It prevents the method from being overridden in a subclass.
• B) It allows the method to be modified.
• C) It makes the method static.
• D) It makes the method abstract.
  Answer: A) It prevents the method from being overridden in a subclass.

69. Which of the following is a valid way to call a method from an interface in Java?

• A) Directly invoking the method from the interface.
• B) Using super to invoke the method from the interface.
• C) Using this to invoke the method from the interface.
• D) Implementing the method in a class and invoking it from an object of that class.
  Answer: D) Implementing the method in a class and invoking it from an object of that class.

70. What is the term for hiding the implementation details of a class and showing only the necessary functionality?

• A) Abstraction
• B) Inheritance
• C) Encapsulation
• D) Polymorphism
  Answer: A) Abstraction

71. What will happen if a subclass attempts to call a private method of its superclass in Java?

• A) It will result in a compilation error.
• B) The method will be called successfully.
• C) It will result in a runtime error.
• D) It will call the method but not display any output.
  Answer: A) It will result in a compilation error.

72. Which of the following correctly describes a static method in Java?

• A) It can only be called by instances of the class.
• B) It can be called using the class name or an object reference.
• C) It can be called only from a method in the same class.
• D) It can access instance variables of the class directly.
  Answer: B) It can be called using the class name or an object reference.

73. What is the effect of making a class “abstract” in Java?

• A) It prevents the class from being instantiated.
• B) It makes the class accessible only within its package.
• C) It automatically defines abstract methods.
• D) It prevents the class from being inherited.
  Answer: A) It prevents the class from being instantiated.

74. In Java, what happens if a subclass does not override a method defined in an interface?

• A) The program will fail to compile.
• B) The subclass will inherit the method from the interface.
• C) The method from the interface will be invoked as-is.
• D) The subclass will be required to implement the method.
  Answer: D) The subclass will be required to implement the method.

75. Which of the following is NOT a valid method for a class to override in Java?

• A) toString()
• B) equals()
• C) hashCode()
• D) clone()
  Answer: D) clone()

76. In Java, what is the difference between an abstract class and an interface?

• A) An abstract class can have concrete methods, while an interface cannot.
• B) An abstract class cannot have methods, while an interface can.
• C) An abstract class can be extended, but an interface cannot.
• D) An interface can be extended by another interface, but an abstract class cannot.
  Answer: A) An abstract class can have concrete methods, while an interface cannot.

77. What is the purpose of the instanceof operator in Java?

• A) To check the type of an object at runtime.
• B) To create a new instance of a class.
• C) To convert one class type into another.
• D) To compare two objects for equality.
  Answer: A) To check the type of an object at runtime.

78. What does method overloading allow you to do in Java?

• A) It allows multiple methods with the same name but different parameter lists.
• B) It allows multiple methods with the same signature.
• C) It allows methods from different classes to be merged.
• D) It allows a method to be invoked using multiple instances.
  Answer: A) It allows multiple methods with the same name but different parameter lists.

79. Which of the following is the primary purpose of the final keyword in Java when applied to a class?

• A) The class cannot be extended.
• B) The class cannot be instantiated.
• C) The class cannot be abstract.
• D) The class can only contain final variables.
  Answer: A) The class cannot be extended.

80. What happens when you invoke super() in a constructor of a subclass in Java?

• A) It calls the constructor of the superclass.
• B) It invokes the constructor of the subclass.
• C) It calls a method from the superclass.
• D) It invokes a constructor of the current class.
  Answer: A) It calls the constructor of the superclass.

81. Which of the following is true about method overriding in Java?

• A) The method signature must match exactly between the superclass and subclass.
• B) The return type must be the same or a subtype of the return type in the superclass.
• C) The overriding method can have a different name from the method in the superclass.
• D) The access modifier can be more restrictive than the superclass method.
  Answer: B) The return type must be the same or a subtype of the return type in the superclass.

82. In which of the following cases will a NullPointerException be thrown in Java?

• A) Calling a method on a null object reference.
• B) Attempting to access an index in an empty array.
• C) Dividing by zero.
• D) Using an undefined variable.
  Answer: A) Calling a method on a null object reference.

83. Which of the following is NOT true about constructors in Java?

• A) A constructor must have the same name as the class.
• B) A constructor can return a value.
• C) A constructor can have parameters.
• D) A constructor is automatically called when an object is created.
  Answer: B) A constructor can return a value.

84. What happens when an object is passed by reference to a method in Java?

• A) A copy of the object is created inside the method.
• B) The original object can be modified inside the method.
• C) The object cannot be modified inside the method.
• D) The method cannot access the object.
  Answer: B) The original object can be modified inside the method.

85. Which of the following is a correct way to create an array of objects in Java?

• A) Object[] arr = new Object[10];
• B) Object arr = new Object[10];
• C) Object arr[] = new Object(10);
• D) Object[] arr = new Object[10];
  Answer: A) Object[] arr = new Object[10];

86. What is the effect of using a protected access modifier for a variable in Java?

• A) The variable is only accessible within its own class.
• B) The variable is accessible by classes within the same package.
• C) The variable is accessible by subclasses and classes in the same package.
• D) The variable is accessible by any class.
  Answer: C) The variable is accessible by subclasses and classes in the same package.

87. What will happen if a subclass does not implement an abstract method of an interface in Java?

• A) The program will compile successfully.
• B) The program will throw a runtime exception.
• C) The program will fail to compile.
• D) The method will be automatically implemented by the superclass.
  Answer: C) The program will fail to compile.

88. Which of the following can be used to prevent method overriding in Java?

• A) protected
• B) private
• C) final
• D) static
  Answer: C) final

89. What does the term “overriding” mean in the context of OOP?

• A) A method in the subclass has the same name, return type, and parameters as a method in the superclass.
• B) A subclass calls a method from its parent class.
• C) A method in the superclass has a different return type than the subclass method.
• D) A subclass replaces the parent class with a new class.
  Answer: A) A method in the subclass has the same name, return type, and parameters as a method in the superclass.

90. What is a common use case of an abstract class in Java?

• A) To define a base class with some method implementations but leave others abstract for subclasses.
• B) To allow objects to be created directly from the abstract class.
• C) To define a class with only static methods.
• D) To define a class that cannot be inherited.
  Answer: A) To define a base class with some method implementations but leave others abstract for subclasses.

 

91. What is the main benefit of using an interface in Java?

• A) To allow multiple inheritance.
• B) To implement abstract methods.
• C) To provide a common set of methods for all implementing classes.
• D) To inherit methods from multiple classes.
  Answer: C) To provide a common set of methods for all implementing classes.

92. Which of the following is true about a static block in Java?

• A) It is executed when an object of the class is created.
• B) It is executed when the class is loaded into memory.
• C) It is executed only once when the class is compiled.
• D) It cannot access static members of the class.
  Answer: B) It is executed when the class is loaded into memory.

93. Which of the following is a key feature of the Singleton Design Pattern?

• A) It ensures a class has only one instance and provides a global point of access to it.
• B) It allows a class to inherit from multiple classes.
• C) It allows a class to have multiple constructors.
• D) It provides a template for other classes to follow.
  Answer: A) It ensures a class has only one instance and provides a global point of access to it.

94. What happens when a subclass does not override a method from its parent class in Java?

• A) The parent class method is inherited by the subclass and used as is.
• B) A compilation error occurs because all methods must be overridden.
• C) The subclass must declare the method as abstract.
• D) The subclass can implement the method with its own logic.
  Answer: A) The parent class method is inherited by the subclass and used as is.

95. What is the primary difference between == and .equals() in Java?

• A) == compares object references, while .equals() compares the content of objects.
• B) == compares the content of objects, while .equals() compares references.
• C) == works only with primitive types, while .equals() works only with objects.
• D) There is no difference between == and .equals().
  Answer: A) == compares object references, while .equals() compares the content of objects.

96. Which of the following best describes a “factory method” in object-oriented design?

• A) A method that initializes an object in a subclass.
• B) A method used to create objects without specifying the exact class of object that will be created.
• C) A method that constructs a class object directly.
• D) A method used to destroy objects after they are no longer needed.
  Answer: B) A method used to create objects without specifying the exact class of object that will be created.

97. Which of the following best defines “composition” in object-oriented programming?

• A) A subclass inherits from a superclass.
• B) A class includes objects of other classes as its members.
• C) A class implements multiple interfaces.
• D) A class defines methods that are implemented by other classes.
  Answer: B) A class includes objects of other classes as its members.

98. In Java, which of the following is true about method overriding?

• A) The method in the subclass must have the same signature as the method in the superclass.
• B) The method in the subclass can have a different name.
• C) The method in the subclass can have a different return type.
• D) Method overriding can occur only with private methods.
  Answer: A) The method in the subclass must have the same signature as the method in the superclass.

99. Which of the following statements about Java’s exception handling is true?

• A) Exception handling is based on the principle of try-catch blocks.
• B) Java does not allow checked exceptions.
• C) Exceptions are only thrown by the throw keyword.
• D) Unchecked exceptions are only used in runtime scenarios.
  Answer: A) Exception handling is based on the principle of try-catch blocks.

100. What does the “abstract” keyword indicate when used on a method in Java?

• A) The method has no implementation in the current class and must be implemented by subclasses.
• B) The method is protected and cannot be overridden.
• C) The method is final and cannot be overridden by subclasses.
• D) The method is static and belongs to the class itself.
  Answer: A) The method has no implementation in the current class and must be implemented by subclasses.

101. In Java, what is the difference between ArrayList and LinkedList?

• A) ArrayList is backed by an array, and LinkedList is backed by a doubly linked list.
• B) ArrayList is slower than LinkedList for inserting and deleting elements.
• C) ArrayList allows faster access to elements compared to LinkedList.
• D) All of the above are true.
  Answer: D) All of the above are true.

102. Which of the following is a characteristic of the Proxy Design Pattern?

• A) It provides a surrogate or placeholder for another object.
• B) It allows objects to be created dynamically.
• C) It ensures that only one instance of a class is created.
• D) It enforces access control to a resource.
  Answer: A) It provides a surrogate or placeholder for another object.

103. Which of the following is true regarding the super() method in Java?

• A) It can be used to call the constructor of a parent class.
• B) It can only be used to access instance variables of the parent class.
• C) It can only be used within a method, not within constructors.
• D) It cannot be used if the class does not have a parent class.
  Answer: A) It can be used to call the constructor of a parent class.

104. Which of the following statements about the clone() method in Java is correct?

• A) The clone() method is used to copy the contents of an object.
• B) The clone() method is a static method that does not require an object instance.
• C) The clone() method must be overridden in every class.
• D) The clone() method is used to create a deep copy of an object automatically.
  Answer: A) The clone() method is used to copy the contents of an object.

105. In object-oriented design, what does the “Liskov Substitution Principle” state?

• A) Objects of a superclass should be replaceable with objects of a subclass without affecting the correctness of the program.
• B) Subclasses should implement methods with the same return type as the superclass.
• C) All subclasses should be abstract classes.
• D) A class should inherit from multiple classes.
  Answer: A) Objects of a superclass should be replaceable with objects of a subclass without affecting the correctness of the program.

106. What is the effect of the static keyword in Java when applied to a variable?

• A) It makes the variable unique to each instance of the class.
• B) It makes the variable shared across all instances of the class.
• C) It makes the variable visible only within the method in which it is defined.
• D) It makes the variable behave like a constant.
  Answer: B) It makes the variable shared across all instances of the class.

107. What is the primary advantage of using the Composite Design Pattern?

• A) It allows clients to treat individual objects and compositions of objects uniformly.
• B) It separates the concerns of object creation and usage.
• C) It provides flexibility for code that deals with collections.
• D) It ensures that objects are only created once.
  Answer: A) It allows clients to treat individual objects and compositions of objects uniformly.

108. Which of the following is a true statement about method signatures in Java?

• A) Method signatures include the method name and parameter types.
• B) Method signatures only include the method name.
• C) Method signatures include the return type and method name.
• D) Method signatures do not include parameter types.
  Answer: A) Method signatures include the method name and parameter types.

109. What is a key advantage of using the Iterator Design Pattern?

• A) It allows sequential access to elements of a collection without exposing the underlying structure.
• B) It allows the modification of the elements while iterating.
• C) It allows direct access to specific elements in a collection.
• D) It eliminates the need for indexing.
  Answer: A) It allows sequential access to elements of a collection without exposing the underlying structure.

110. In Java, what does the finally block do in exception handling?

• A) It is executed regardless of whether an exception was thrown or not.
• B) It is executed only if an exception is thrown.
• C) It is executed only if no exception is thrown.
• D) It prevents exceptions from being thrown.
  Answer: A) It is executed regardless of whether an exception was thrown or not.

 

111. What is the purpose of the transient keyword in Java?

• A) It indicates that a variable should not be serialized.
• B) It makes a variable available to all subclasses.
• C) It marks a method as private.
• D) It makes a variable constant across all instances of the class.
  Answer: A) It indicates that a variable should not be serialized.

112. Which of the following is true about the default method in Java interfaces (introduced in Java 8)?

• A) It allows interfaces to have method implementations.
• B) It is used to define a constructor in an interface.
• C) It makes a method static.
• D) It prevents a class from implementing multiple interfaces.
  Answer: A) It allows interfaces to have method implementations.

113. What is the key benefit of using the Strategy Design Pattern?

• A) It allows algorithms to be defined at runtime and replaced easily.
• B) It provides a way to make objects immutable.
• C) It creates a global access point for an object.
• D) It allows the construction of objects with a complex structure.
  Answer: A) It allows algorithms to be defined at runtime and replaced easily.

114. Which of the following methods is used to obtain a thread’s current execution state in Java?

• A) Thread.currentState()
• B) Thread.getState()
• C) Thread.currentThread()
• D) Thread.getPriority()
  Answer: B) Thread.getState()

115. In Java, which of the following classes is used to implement a thread-safe collection?

• A) ArrayList
• B) Vector
• C) HashMap
• D) LinkedList
  Answer: B) Vector

116. Which of the following best describes the Adapter Design Pattern?

• A) It allows incompatible interfaces to work together.
• B) It ensures a class has only one instance.
• C) It allows the class behavior to change dynamically.
• D) It allows different types of objects to be treated uniformly.
  Answer: A) It allows incompatible interfaces to work together.

117. In Java, which of the following statements about abstract classes is true?

• A) An abstract class can have concrete methods (methods with implementation).
• B) An abstract class cannot have any methods with implementation.
• C) An abstract class must only contain static methods.
• D) An abstract class cannot have constructors.
  Answer: A) An abstract class can have concrete methods (methods with implementation).

118. What is the purpose of the volatile keyword in Java?

• A) It ensures that a variable is shared between threads.
• B) It makes a variable constant during the runtime.
• C) It allows a variable to be accessed without synchronization.
• D) It makes a variable immutable.
  Answer: A) It ensures that a variable is shared between threads.

119. Which of the following is true about the java.util.concurrent package in Java?

• A) It provides support for multi-threading and concurrent programming.
• B) It is used only for network programming.
• C) It includes classes that are used exclusively for creating user interfaces.
• D) It is used for object serialization.
  Answer: A) It provides support for multi-threading and concurrent programming.

120. In Java, which of the following is true about an anonymous inner class?

• A) It is a class defined within a method with no name.
• B) It is a type of static inner class.
• C) It can only be used for event handling.
• D) It must be declared as final.
  Answer: A) It is a class defined within a method with no name.

121. Which of the following is the best description of the Observer Design Pattern?

• A) It allows one object to notify a list of dependent objects automatically.
• B) It allows a class to modify its behavior at runtime.
• C) It provides a way to combine multiple objects into a single object.
• D) It hides the details of a system’s complexity from users.
  Answer: A) It allows one object to notify a list of dependent objects automatically.

122. Which of the following is the main purpose of the “Builder” Design Pattern?

• A) To construct a complex object step by step.
• B) To ensure that a class has only one instance.
• C) To separate the creation of an object from its usage.
• D) To define a family of algorithms.
  Answer: A) To construct a complex object step by step.

123. In Java, what is the effect of the synchronized keyword?

• A) It makes the method or block thread-safe by allowing only one thread to access it at a time.
• B) It prevents a method from being inherited by subclasses.
• C) It makes the method static.
• D) It ensures that the method is executed in a separate thread.
  Answer: A) It makes the method or block thread-safe by allowing only one thread to access it at a time.

124. What does the term “polymorphism” mean in object-oriented programming?

• A) The ability of different objects to respond to the same message in different ways.
• B) The ability of a class to inherit methods and attributes from another class.
• C) The ability to combine multiple objects into one.
• D) The ability of a class to implement multiple interfaces.
  Answer: A) The ability of different objects to respond to the same message in different ways.

125. Which of the following is a disadvantage of using multiple inheritance in Java?

• A) It can lead to ambiguity and conflicts in method inheritance.
• B) It makes the code easier to understand.
• C) It can improve the performance of the application.
• D) It allows easier debugging.
  Answer: A) It can lead to ambiguity and conflicts in method inheritance.

126. In Java, which of the following will result in a compilation error when using an interface?

• A) Defining instance variables in the interface.
• B) Implementing multiple interfaces in a class.
• C) Using default methods in the interface.
• D) Using the extends keyword to inherit an interface.
  Answer: A) Defining instance variables in the interface.

127. What is the key feature of the Command Design Pattern?

• A) It encapsulates a request as an object, thus allowing for parameterization of clients with queues, requests, and operations.
• B) It creates a global point of access to an object.
• C) It allows a class to have multiple constructors.
• D) It defines methods that can be invoked by external classes.
  Answer: A) It encapsulates a request as an object, thus allowing for parameterization of clients with queues, requests, and operations.

128. Which of the following is true about the Object.clone() method in Java?

• A) It creates a shallow copy of the object by default.
• B) It cannot be overridden.
• C) It only works for primitive types.
• D) It is automatically invoked when an object is created.
  Answer: A) It creates a shallow copy of the object by default.

129. Which of the following best describes the Facade Design Pattern?

• A) It provides a simplified interface to a complex system of classes.
• B) It creates an object for each element in a system.
• C) It allows clients to interact with multiple systems simultaneously.
• D) It implements a specific algorithm for each client.
  Answer: A) It provides a simplified interface to a complex system of classes.

130. What is the purpose of the java.util.Optional class in Java?

• A) It is used to represent a value that may or may not be present.
• B) It is used for working with streams of data.
• C) It is used to represent a value that is always present.
• D) It provides methods for handling thread synchronization.
  Answer: A) It is used to represent a value that may or may not be present.

 

131. Which of the following statements about Java interfaces is true?

• A) An interface can extend multiple other interfaces.
• B) An interface can extend a class.
• C) An interface cannot contain any methods.
• D) An interface can contain both instance and static variables.
  Answer: A) An interface can extend multiple other interfaces.

132. What is the main advantage of using the Composite Design Pattern?

• A) It allows you to treat individual objects and compositions of objects uniformly.
• B) It guarantees that objects are always mutable.
• C) It ensures that each object is initialized before it is used.
• D) It provides a mechanism for creating objects dynamically at runtime.
  Answer: A) It allows you to treat individual objects and compositions of objects uniformly.

133. Which of the following is true about Java’s static keyword?

• A) It allows a method or variable to belong to the class rather than any instance of the class.
• B) It can only be used in static nested classes.
• C) It ensures that a method or variable is synchronized.
• D) It makes a method or variable accessible only within the class in which it is declared.
  Answer: A) It allows a method or variable to belong to the class rather than any instance of the class.

134. What does it mean when a class is said to be “immutable”?

• A) Its state cannot be modified after it is created.
• B) It cannot be inherited by other classes.
• C) It cannot contain any methods.
• D) It can only have a single constructor.
  Answer: A) Its state cannot be modified after it is created.

135. What is the purpose of using the final keyword in Java?

• A) It is used to prevent a method from being overridden or a class from being subclassed.
• B) It allows a method to be used asynchronously.
• C) It is used to initialize instance variables only.
• D) It makes a class thread-safe.
  Answer: A) It is used to prevent a method from being overridden or a class from being subclassed.

136. Which of the following statements is true about the Singleton Design Pattern?

• A) It ensures that a class has only one instance and provides a global point of access to it.
• B) It allows multiple instances of a class to be created dynamically.
• C) It helps in creating independent objects that do not rely on each other.
• D) It provides a mechanism for creating objects using factory methods.
  Answer: A) It ensures that a class has only one instance and provides a global point of access to it.

137. Which of the following is a characteristic of a deep copy of an object in Java?

• A) A deep copy creates an independent copy of the object and all objects it refers to.
• B) A deep copy is only applicable to primitive types.
• C) A deep copy shares references to the objects in the original instance.
• D) A deep copy only works for arrays.
  Answer: A) A deep copy creates an independent copy of the object and all objects it refers to.

138. What does the term “encapsulation” mean in object-oriented programming?

• A) The concept of hiding the internal state and requiring all interaction to be performed through methods.
• B) The process of combining multiple classes into a single class.
• C) The inheritance of properties and methods from a superclass.
• D) The ability of a class to have multiple constructors.
  Answer: A) The concept of hiding the internal state and requiring all interaction to be performed through methods.

139. Which of the following Java collection classes is synchronized and thread-safe?

• A) ArrayList
• B) HashMap
• C) Hashtable
• D) LinkedHashMap
  Answer: C) Hashtable

140. Which design pattern is typically used to decouple the creation of an object from its use, especially when the exact type of object is not known until runtime?

• A) Factory Method Pattern
• B) Singleton Pattern
• C) Proxy Pattern
• D) Observer Pattern
  Answer: A) Factory Method Pattern

141. What is the main purpose of the super keyword in Java?

• A) It refers to the immediate parent class of the current object.
• B) It invokes the current method recursively.
• C) It prevents a subclass from accessing the superclass.
• D) It refers to the current instance of a class.
  Answer: A) It refers to the immediate parent class of the current object.

142. Which of the following is the purpose of the java.io.Serializable interface in Java?

• A) It allows objects to be serialized and written to an output stream.
• B) It provides an API for handling network operations.
• C) It allows objects to be cloned.
• D) It ensures that classes are thread-safe.
  Answer: A) It allows objects to be serialized and written to an output stream.

143. What does it mean to override a method in Java?

• A) It means defining a new version of a method in a subclass that replaces the inherited method.
• B) It means creating a new method in the superclass.
• C) It means making a method static.
• D) It means defining a method in the interface.
  Answer: A) It means defining a new version of a method in a subclass that replaces the inherited method.

144. Which of the following is a feature of the Prototype Design Pattern?

• A) It allows objects to be cloned or copied at runtime.
• B) It ensures that a class has only one instance.
• C) It separates the creation of an object from its usage.
• D) It allows a class to be created dynamically.
  Answer: A) It allows objects to be cloned or copied at runtime.

145. What is the purpose of the instanceof operator in Java?

• A) It is used to check if an object is an instance of a specific class or interface.
• B) It is used to create a new instance of an object.
• C) It is used to compare the equality of two objects.
• D) It is used to clone an object.
  Answer: A) It is used to check if an object is an instance of a specific class or interface.

146. What is the main disadvantage of using the Factory Design Pattern?

• A) It can lead to an increased number of classes and complexity.
• B) It is difficult to implement with polymorphism.
• C) It does not provide flexibility in object creation.
• D) It makes the system less flexible.
  Answer: A) It can lead to an increased number of classes and complexity.

147. Which of the following is true about the Object.equals() method in Java?

• A) It checks if two objects are logically equal (based on their state).
• B) It checks if two objects are the same instance.
• C) It checks if two objects are of the same class.
• D) It cannot be overridden by subclasses.
  Answer: A) It checks if two objects are logically equal (based on their state).

148. Which of the following is a feature of the State Design Pattern?

• A) It allows an object to change its behavior when its internal state changes.
• B) It is used to modify the behavior of methods dynamically.
• C) It ensures that only one instance of a class is created.
• D) It allows a class to adapt to multiple inheritance.
  Answer: A) It allows an object to change its behavior when its internal state changes.

149. What does the term “inheritance” mean in object-oriented programming?

• A) The process by which one class can inherit properties and methods from another class.
• B) The concept of hiding the internal details of a class.
• C) The ability of objects to respond to the same method in different ways.
• D) The process of creating an object from a class.
  Answer: A) The process by which one class can inherit properties and methods from another class.

150. Which of the following is true about the finalize() method in Java?

• A) It is called by the garbage collector before an object is removed from memory.
• B) It is used to mark methods as unchangeable.
• C) It ensures that the memory allocated to an object is deallocated immediately.
• D) It is used to lock the methods of a class for thread safety.
  Answer: A) It is called by the garbage collector before an object is removed from memory.