1. What is Java?

2. What are the basic data types in Java?

3. What is an if-else statement in Java?

4. What is a switch statement in Java?

5. What is a for loop in Java?

6. How does a while loop work in Java?

7. What is the purpose of the do-while loop?

8. How do you declare a variable in Java?

9. What is a class in Java?

10. What is an object in Java?

11. How does inheritance work in Java?

12. What is polymorphism in Java?

13. What are constructors in Java?

14. What is method overloading?

15. What is encapsulation in Java?

16. What are access modifiers?

17. What is an interface in Java?

18. What is an abstract class in Java?

19. How does exception handling work in Java?

20. What is a try-catch block?

21. How do you define an array in Java?

22. What is a for-each loop in Java?

23. What is a Java ArrayList?

24. How does a HashMap work in Java?

25. What is an Iterator in Java?

26. What is the purpose of the Collections framework?

27. What is multithreading in Java?

28. How does the synchronized keyword work?

29. What is a lambda expression in Java?

30. What is a functional interface?

31. What is the Stream API in Java?

32. How does the filter method work in a Java Stream?

33. What is method reference in Java?

34. What is serialization in Java?

35. What is a singleton class in Java?

36. What is the difference between List and Set?

37. How does the map method work in Java streams?

38. What is a default method in interfaces?

39. How does the reduce method work in Java streams?

40. What are Optional types in Java?

41. What is reflection in Java?

42. How does garbage collection work in Java?

43. What is the difference between '==' and 'equals()' in Java?

44. How does the try-with-resources statement work?

45. What is a JDBC in Java?