🔹 Core Java
1. What is JVM, JRE, and JDK? Explain the difference.
2. Why is Java platform-independent?
3. What is an abstract class?
4. What is an interface?
5. What is the difference between an abstract class and a concrete class?
6. What is a constructor? What are its types?
7. What is an exception in Java?
8. What are the types of exceptions in Java?
9. How to create a user-defined exception?
10. When does a NullPointerException occur?
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🔹 Collections
11. What is a Collection in Java?
12. Why use Collection instead of arrays?
13. Difference between Array and ArrayList
14. Difference between Vector and HashSet
15. What is a Map in Java? What are its types?
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🔹 String & Threads
16. What is a String? Why is String immutable?
17. What is a thread in Java?
18. What is synchronization?
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🔹 JDBC
19. How to connect a Java application with a database using JDBC?
20. Difference between Statement and PreparedStatement
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🔹 Java 8
21. What is JDK 1.8? What are its features?
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🔹 Spring Framework
22. What is IoC container? What are its types?
23. What is Spring Context?
24. What is a Bean in Spring?
25. What is Dependency Injection?
26. What is @Autowired annotation?
27. Difference between BeanFactory and ApplicationContext
28. What is AOP (Aspect-Oriented Programming)?
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🔹 Hibernate & JPA
29. What is the difference between Hibernate and JPA?
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🔹 Coding
30. Write code to find the occurrence of each character in a string.