Here's a set of 100 questions covering a wide range of theoretical and practical aspects of Java programming:

Core Java Concepts:

1. What is the difference between JDK, JRE, and JVM?

2. Explain the difference between == and equals() method in Java.

3. What is a Java package and how is it used?

4. Describe the principles of Object-Oriented Programming (OOP) in Java.

5. What is the significance of the main() method in Java?

6. Explain the concept of method overloading and method overriding.

7. What are access modifiers in Java and how are they used?

8. Describe the difference between abstract classes and interfaces.

9. Explain the purpose of the final keyword in Java.

10. How does Java support multithreading?

Collections Framework:

11. List the main interfaces in the Java Collections Framework.

12. Explain the differences between ArrayList and LinkedList.

13. What is a HashMap in Java and how does it work?

14. How are HashSet and TreeSet different in Java?

15. Describe the purpose of the Iterator interface in Java.

Exception Handling:

16. What are checked and unchecked exceptions in Java?

17. Explain the try-catch-finally blocks in Java.

18. How do you create custom exceptions in Java?

19. Describe the difference between throw and throws in Java.

20. Explain the concept of exception chaining in Java.

Input/Output:

21. How do you read input from the console in Java?

22. Explain the purpose of FileReader and FileWriter classes.

23. What are the differences between InputStream and OutputStream?

24. How does Java support serialization and deserialization?

25. What is the purpose of the java.io package in Java?

Multithreading:

26. What is a thread in Java?

27. Explain the difference between Thread class and Runnable interface.

28. How do you create and start a thread in Java?

29. Describe synchronization in Java and why it's necessary.

30. What are the main methods of the Object class related to multithreading?

JDBC and Database Connectivity:

31. What is JDBC and how does it facilitate database connectivity?

32. Explain the steps involved in connecting to a database using JDBC.

33. Describe PreparedStatement and CallableStatement in JDBC.

34. What is the purpose of ResultSet in JDBC?

35. How do you handle transactions in JDBC?

Networking:

36. What is a socket in Java networking?

37. Explain the difference between TCP and UDP protocols.

38. How do you create a client-server application in Java?

39. Describe InetAddress and its usage in Java networking.

40. What is the purpose of URL and URLConnection classes in Java?

GUI Development:

41. Describe Swing and its role in Java GUI development.

42. What are the main components of a Swing GUI application?

43. How do you handle events in Swing?

44. Explain the purpose of layout managers in Swing.

45. What is the difference between AWT and Swing in Java?

Design Patterns:

46. Describe the Singleton design pattern and its implementation in Java.

47. Explain the Factory Method design pattern with an example.

48. What is the Observer design pattern and when is it used?

49. Describe the Model-View-Controller (MVC) design pattern.

50. How do you implement the Strategy design pattern in Java?

Advanced Java Concepts:

51. What are generics in Java and why are they used?

52. Explain the concept of lambda expressions in Java.

53. How do you use streams in Java for functional programming?

54. Describe the purpose of the java.util.concurrent package.

55. What are annotations in Java and how are they used?

Testing and Build Tools:

56. Describe the purpose of JUnit in Java testing.

57. How do you write and run unit tests using JUnit?

58. Explain the concept of mock objects in testing.

59. What is Test-Driven Development (TDD) and its benefits?

60. How do you use Maven for project management and build automation?

Web Development:

61. Describe the role of servlets in Java web development.

62. What is JSP and how is it different from servlets?

63. Explain the purpose of JavaBeans in web development.

64. How do you handle sessions and cookies in servlets?

65. Describe the MVC architecture in web applications.

Security:

66. What are the main security vulnerabilities in Java applications?

67. Explain the purpose of SSL/TLS in Java security.

68. How do you prevent SQL injection attacks in Java?

69. Describe best practices for secure password storage in Java.

70. What is Cross-Site Scripting (XSS) and how do you prevent it in Java?

Performance Optimization:

71. Describe common techniques for optimizing Java code.

72. How do you profile Java applications for performance analysis?

73. What are JIT compilers and how do they improve Java performance?

74. Explain the purpose of caching in Java applications.

75. Describe best practices for memory management in Java.

Tools and Libraries:

76. What is Apache Kafka and how is it used in Java applications?

77. Describe the purpose of Apache Hadoop in big data processing.

78. How do you use Apache Tomcat for deploying Java web applications?

79. Explain the role of Hibernate in Java persistence.

80. What is Spring Framework and its core modules?

Frameworks and Libraries:

81. Describe the purpose of Spring Boot in Java application development.

82. How do you configure Spring MVC for RESTful web services?

83. What is Jackson library and its role in JSON processing?

84. Explain the purpose of JPA and its implementation in Java EE.

85. How do you integrate Spring Security into a Java web application?

Advanced Topics:

86. Describe the principles of reactive programming in Java.

87. What are microservices and how do you implement them in Java?

88. Explain the purpose of Docker and Kubernetes in Java deployment.

89. How do you use Java Reflection for dynamic code execution?

90. Describe the purpose of bytecode manipulation libraries in Java.

Data Structures and Algorithms:

91. Describe the characteristics of a binary search tree.

92. How do you implement depth-first search (DFS) in Java?

93. Explain the concept of dynamic programming with an example.

94. What is the purpose of a priority queue in Java?

95. How do you implement a hash table in Java?

Concurrency:

96. Explain the purpose of concurrent data structures in Java.

97. How do you use locks and conditions for thread synchronization?

98. Describe= the concept of thread pools and their benefits.

99. What is the purpose of the java.util.concurrent package in Java?

100. How do you handle deadlock situations in Java?

These questions cover a broad spectrum of Java programming, ranging from fundamental concepts to advanced topics and practical applications. Answering them will not only test your theoretical knowledge but also your practical understanding and experience with Java programming.