Java Interview Questions For Automation Testers

1. What is a class?

2. What is the difference between heap and stack?

3. What is the difference between instance variable and a local variable?

4. What is Constructor? Types of Constructor?

5. Difference between Break and Continue?

6. To exit the system from the current execution what command is used in java?

7. Addition features in Java 8?

8. Difference between for and foreach loops in java and use of it?

9. Can we have multiple public class within a class?

10. What is inheritance? Types of inheritance? Does multiple inheritances allow in java? If not, why?

11. What is polymorphism? How we can achieve it? 

12. Difference between method overloading and method overriding?

13. Can we achieve method overloading when two methods have an only difference in return type?

14. Method overloading and overriding examples in the Selenium project?

15. What is encapsulation?

16. What are IS-A and HAS-A relation in java With examples?

17. What is final and super keyword? Difference between them?

18. Explain runtime polymorphism and compile-time with examples?

19. Can the final/Static method be overloaded?

20. Can final/Static methods be overridden?

21. Can we overload the main method?

22. Can we execute a class without a main method?

23. What is Package?

24. What is an Abstract Class? Write an example code?

25. What is an Interface? What is the difference from the Abstract class?

26. Can we use private and protect access modified inside an Interface?

27. Can multiple inheritances support in Interface?

28. Examples of Abstract and Interface used in the selenium project?

29. What is Exception and what is the base class of it?

30. What is Final, Finally, Finalize?

31. What is done in finally block?

32. What is garbage collection java? How it is done?

33. What is the difference between Throws and Throw?

34. Gives some examples of java and Selenium?

35. What is Java Reflection, Singleton?

36. What is threading? How does multithreading achieve? How to initiate a thread in java? What do you mean by thread-safe?

37. What is the difference between collection and collections?

38. collection type in java?

39. Difference between Array and ArrayList?

40. Difference between Set and HashSet?

41. Difference between HashMap and HasTable?

42. Difference between ArrayList and LinkList?

43. How do you use Map collection your project?

44. Can we have a duplicate key value in HasMap?

45. How to fetch values from a hashmap?

46. Difference between String, StringBuilder and StringBuffer?

#Java #Programs

1. Write a Code to generate Random numbers.

2. Write code to verify a number is a perfect number or not.

3. Fibonacci series from 1 to 10.

4. Write a program to find a Factorial of a number.

5. Swap two number s without using the third variable.

6. Program to find the greatest of three numbers.

7. An Array of numbers given. .Find the largest two number and print it

8. Reverse a number.

9. Verify if a given number is a palindrome or not.(same concept of reversing a number)

10. Armstrong number program.

11. A String is given to remove the white spaces, reverse it and print the only odd position characters.

12. Check if a string is an anagram of another string.

13. A string is given make few characters to upper case as asked.

14. In a String print the occurrence of each character.

15. In a Statement check how any duplicate strings are there and remove them.

16. Use split to print each word of a statement.

17. Find the substring of a String.

18. Remove duplicate characters from a string and print it.

19. Write a code to print the triangle of numbers.

20. Read and Write file program.

21. Calculate the power of a number using a while loop