⭐ Top 100 Java MCQ Questions and Answers (Beginner to Advanced)

 

Java remains one of the most popular programming languages for application development, enterprise systems, backend services, testing frameworks, and more. Whether you're preparing for a coding interview, certification, or improving your fundamentals, practicing MCQs is one of the most effective ways to strengthen your understanding.

Below are the top 100 most important Java multiple-choice questions, carefully selected for students, professionals, and interview aspirants.

 

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✅ Top 100 Java MCQs With Answers

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1–20: Java Basics

1. Java is a ___ language.
   A. Low-level
   B. High-level
   C. Assembly
   D. Machine
   Answer: B

2. Who invented Java?
   A. James Gosling
   B. Dennis Ritchie
   C. Guido van Rossum
   D. Ken Thompson
   Answer: A

3. JVM stands for:
   A. Java Virtual Machine
   B. Java Variable Method
   C. Joint Virtual Module
   D. Java Verified Model
   Answer: A

4. Which company originally developed Java?
   A. Sun Microsystems
   B. Oracle
   C. IBM
   D. Microsoft
   Answer: A

5. Java source files use extension:
   A. .jav
   B. .class
   C. .java
   D. .jv
   Answer: C

6. Bytecode file extension:
   A. .java
   B. .class
   C. .exe
   D. .jar
   Answer: B

7. Which keyword is used to define a class?
   A. type
   B. struct
   C. class
   D. define
   Answer: C

8. Java is:
   A. Platform-dependent
   B. Platform-independent
   C. Hardware-dependent
   D. None
   Answer: B

9. Which of the following is NOT a Java feature?
   A. Object-oriented
   B. Robust
   C. High performance
   D. Use of pointers
   Answer: D

10. Which tool compiles Java code?
    A. jvm
    B. javac
    C. jcompile
    D. jrun
    Answer: B

11. Which keyword prevents inheritance?
    A. final
    B. static
    C. constant
    D. protected
    Answer: A

12. JRE stands for:
    A. Java Runtime Environment
    B. Java Real Engine
    C. Java Runtime Execution
    D. Java Ready Environment
    Answer: A

13. Which method starts Java execution?
    A. start()
    B. main()
    C. run()
    D. init()
    Answer: B

14. Arrays in Java are:
    A. Objects
    B. Primitives
    C. Methods
    D. None
    Answer: A

15. Java uses ___ for memory management.
    A. Destructor
    B. Garbage Collector
    C. Manual free command
    D. Pointer free
    Answer: B

16. Which is NOT a Java primitive?
    A. int
    B. float
    C. String
    D. boolean
    Answer: C

17. Java strings are:
    A. Mutable
    B. Immutable
    C. Static
    D. Volatile
    Answer: B

18. Which loop is exit-controlled?
    A. for
    B. while
    C. do-while
    D. foreach
    Answer: C

19. Java package keyword:
    A. pkg
    B. package
    C. import
    D. include
    Answer: B

20. Default value of int:
    A. 0
    B. null
    C. undefined
    D. garbage value
    Answer: A

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21–40: OOP Concepts

21. Java is fully OOP except for:
    A. Arrays
    B. Primitives
    C. Strings
    D. Packages
    Answer: B

22. Runtime polymorphism is achieved using:
    A. Overloading
    B. Overriding
    C. Abstraction
    D. Encapsulation
    Answer: B

23. Which keyword is used for inheritance?
    A. implements
    B. extends
    C. inherits
    D. use
    Answer: B

24. Interfaces contain:
    A. Only constants
    B. Only abstract methods
    C. Both A and B
    D. None
    Answer: C

25. A class that cannot be instantiated:
    A. static class
    B. abstract class
    C. final class
    D. private class
    Answer: B

26. Multiple inheritance in Java is achieved using:
    A. Classes
    B. Interfaces
    C. Abstract classes
    D. Static members
    Answer: B

27. Which binding is used for method overloading?
    A. Late binding
    B. Early binding
    C. Runtime binding
    D. None
    Answer: B

28. Encapsulation means:
    A. Wrapping data and methods together
    B. Hiding code
    C. Data duplication
    D. None
    Answer: A

29. Which allows implementation of multiple interfaces?
    A. class A implements B, C
    B. class A extends B, C
    C. class A extends B implements C, D
    D. None
    Answer: A

30. Private members are accessible in:
    A. Same class
    B. Same package
    C. Subclasses
    D. Everywhere
    Answer: A

31. Method overriding occurs in:
    A. Same class
    B. Parent-child classes
    C. Static methods
    D. Final classes
    Answer: B

32. Constructor return type:
    A. void
    B. int
    C. String
    D. None
    Answer: D

33. Final variable means:
    A. Changeable
    B. Constant
    C. Temporary
    D. Dynamic
    Answer: B

34. A method inside an interface is by default:
    A. private
    B. abstract
    C. static
    D. final
    Answer: B

35. Constructor overloading means:
    A. Multiple constructors
    B. One constructor
    C. Static constructor
    D. Final constructor
    Answer: A

36. Which is not access modifier?
    A. public
    B. private
    C. friendly
    D. protected
    Answer: C

37. super keyword refers to:
    A. Current class
    B. Parent class
    C. Interface
    D. Static method
    Answer: B

38. Upcasting is:
    A. Child → Parent
    B. Parent → Child
    C. Object → Class
    D. None
    Answer: A

39. Downcasting requires:
    A. Automatic conversion
    B. Explicit cast
    C. No cast
    D. None
    Answer: B

40. Which class is root of Java hierarchy?
    A. Object
    B. Class
    C. System
    D. Main
    Answer: A

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41–60: Java Collections / Strings

41. StringBuilder is:
    A. Mutable
    B. Immutable
    C. Static
    D. Constant
    Answer: A

42. HashMap stores elements as:
    A. Key-value
    B. Indexed
    C. Sorted
    D. Priority
    Answer: A

43. ArrayList belongs to which package?
    A. java.io
    B. java.util
    C. java.net
    D. java.lang
    Answer: B

44. Which collection is synchronized?
    A. ArrayList
    B. Vector
    C. HashSet
    D. HashMap
    Answer: B

45. Set allows:
    A. Duplicates
    B. No duplicates
    C. Only integers
    D. Sorted values
    Answer: B

46. Which interface does not allow duplicate values?
    A. List
    B. Set
    C. Map
    D. Iterator
    Answer: B

47. LinkedList allows:
    A. Random access
    B. Fast insert/delete
    C. No null values
    D. Sorted order
    Answer: B

48. HashSet uses:
    A. Tree
    B. Hash table
    C. Array
    D. Stack
    Answer: B

49. Stack follows:
    A. FIFO
    B. LIFO
    C. FILO
    D. Random
    Answer: B

50. Queue follows:
    A. LIFO
    B. FIFO
    C. FILO
    D. Both
    Answer: B

51. Which is fastest for search?
    A. ArrayList
    B. HashSet
    C. TreeSet
    D. LinkedList
    Answer: B

52. StringBuffer is:
    A. Thread-safe
    B. Not thread-safe
    C. Immutable
    D. None
    Answer: A

53. equals() checks:
    A. Reference
    B. Content
    C. Hashcode
    D. None
    Answer: B

54. == operator checks:
    A. Reference
    B. Value
    C. Type
    D. None
    Answer: A

55. Collections.sort() works on:
    A. Map
    B. List
    C. Set
    D. Iterator
    Answer: B

56. Which allows null key?
    A. TreeMap
    B. HashMap
    C. Hashtable
    D. EnumMap
    Answer: B

57. Hashtable is:
    A. Synchronized
    B. Not synchronized
    C. Immutable
    D. Obsolete
    Answer: A

58. TreeSet stores data in:
    A. Hash table
    B. Balanced tree
    C. Graph
    D. Array
    Answer: B

59. ListIterator allows:
    A. Forward traversal only
    B. Backward traversal only
    C. Both directions
    D. None
    Answer: C

60. remove() on list removes element by:
    A. Key
    B. Index
    C. Type
    D. Class
    Answer: B

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61–80: Exception Handling / Threads

61. Which is not a Java exception type?
    A. Checked
    B. Unchecked
    C. Error
    D. Warning
    Answer: D

62. Division by zero causes:
    A. IOException
    B. ArithmeticException
    C. NullPointerException
    D. RuntimeError
    Answer: B

63. finally block executes:
    A. Always
    B. Never
    C. Only on error
    D. On return only
    Answer: A

64. Custom exception extends:
    A. Error
    B. Exception
    C. Throwable
    D. Object
    Answer: B

65. Thread is created by:
    A. Extending Thread
    B. Implementing Runnable
    C. Both A and B
    D. None
    Answer: C

66. Sleep() belongs to:
    A. Runnable
    B. Thread
    C. Object
    D. String
    Answer: B

67. wait() belongs to:
    A. Thread
    B. Object
    C. System
    D. Runtime
    Answer: B

68. Which makes method synchronized?
    A. secure
    B. synchronized
    C. threadsafe
    D. atomic
    Answer: B

69. Deadlock happens when:
    A. Threads wait forever
    B. CPU stops
    C. Memory is low
    D. None
    Answer: A

70. Thread priority range:
    A. 1–5
    B. 1–10
    C. 1–100
    D. 1–MAX
    Answer: B

71. InterruptedException is:
    A. Runtime exception
    B. Checked exception
    C. Error
    D. None
    Answer: B

72. start() invokes:
    A. Constructor
    B. run() in a new thread
    C. main()
    D. sleep()
    Answer: B

73. run() invoked directly:
    A. Starts new thread
    B. Runs in same thread
    C. Stops JVM
    D. None
    Answer: B

74. Thread-safe class example:
    A. ArrayList
    B. Vector
    C. HashMap
    D. StringBuilder
    Answer: B

75. ExecutorService belongs to:
    A. java.lang
    B. java.util.concurrent
    C. java.executor
    D. java.thread
    Answer: B

76. try without catch must have:
    A. throw
    B. finally
    C. return
    D. print
    Answer: B

77. catch block handles:
    A. Errors only
    B. Exceptions only
    C. Warnings only
    D. None
    Answer: B

78. Which stops a thread?
    A. stop()
    B. destroy()
    C. kill()
    D. None
    Answer: D
    (stop() is deprecated)

79. A daemon thread is:
    A. User thread
    B. Background thread
    C. Main thread
    D. Invalid
    Answer: B

80. Number of threads in Java by default:
    A. Only main
    B. main + GC
    C. System-defined
    D. None
    Answer: C

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81–100: File I/O, JDBC, Advanced

81. java.io package deals with:
    A. Networking
    B. Input/output
    C. Database
    D. Web apps
    Answer: B

82. FileReader reads:
    A. Bytes
    B. Characters
    C. Booleans
    D. Streams
    Answer: B

83. FileInputStream reads:
    A. Characters
    B. Bytes
    C. Strings
    D. Files only
    Answer: B

84. Serialization uses:
    A. serialVersionUID
    B. static ID
    C. hashcode
    D. finalize
    Answer: A

85. JDBC stands for:
    A. Java Database Connectivity
    B. Java Data Compiler
    C. Json DB Connector
    D. None
    Answer: A

86. JDBC driver type most common:
    A. Type 1
    B. Type 2
    C. Type 3
    D. Type 4
    Answer: D

87. PreparedStatement prevents:
    A. SQL Injection
    B. Deadlock
    C. Memory leak
    D. Constructors
    Answer: A

88. commit() belongs to:
    A. ResultSet
    B. Connection
    C. DriverManager
    D. Statement
    Answer: B

89. finalize() runs during:
    A. Compilation
    B. Garbage collection
    C. Execution
    D. Shutdown
    Answer: B

90. Reflection allows:
    A. Runtime inspection
    B. Faster code
    C. Memory increase
    D. Compilation
    Answer: A

91. Java annotations start with:
    A. #
    B. @
    C. $
    D. %
    Answer: B

92. Lambda expressions introduced in:
    A. Java 5
    B. Java 6
    C. Java 7
    D. Java 8
    Answer: D

93. Optional class introduced in:
    A. Java 7
    B. Java 8
    C. Java 9
    D. Java 11
    Answer: B

94. Stream API operates on:
    A. Collections
    B. Arrays
    C. Both
    D. None
    Answer: C

95. JAR stands for:
    A. Java Archive
    B. Java Application Resource
    C. Java Repository
    D. None
    Answer: A

96. Which API used for date/time (modern)?
    A. java.util.Date
    B. java.sql.Date
    C. java.time
    D. java.timezone
    Answer: C

97. Which runs fastest?
    A. for loop
    B. stream()
    C. parallelStream()
    D. while loop
    Answer: C

98. Which collects stream results?
    A. Collectors.toList()
    B. Collect()
    C. Reduce()
    D. Output()
    Answer: A

99. Java supports which paradigm?
    A. OOP only
    B. Functional + OOP
    C. Procedural only
    D. None
    Answer: B

100. Java main method must be:
     A. public
     B. static
     C. void
     D. All of the above
     Answer: D

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