Top 90+ Interview Questions for Java developer | iMocha

Java developers are among the most sought-after programming professionals, and companies are constantly on the lookout for talented developers.

However, finding the right talent can be difficult. It requires recruiters to have sound knowledge of the technical and non-technical skills essential for Java roles.

With the right set of knowledge, recruiters can ask the right questions to discover the potential candidate for the role.

So, if you're wondering what questions to ask a Java developer, here is the list of the top 50 interview questions. The questions cover Java's basic, core, and advanced fundamentals and are categorized based on years of experience for your ease.

Top 20 Interview Questions for Java Developers

1. What are the main features of Java?

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

3. What are the access modifiers in Java?

4. What is inheritance, and how does it work in Java?

5. What is polymorphism, and how is it achieved in Java?

6. What is an abstraction, and how is it achieved in Java?

7. What is encapsulation, and how is it achieved in Java?

8. What is an object in Java?

9. What is a constructor in Java?

10. What is a method in Java?

11. What is the difference between method overloading and method overriding in Java?

12. What is a static method in Java?

13. What is an abstract class in Java?

14. What is the interface in Java?

15. What is the difference between abstract class and interface in Java?

16. What is the difference between ArrayList and LinkedList in Java?

17. What is the difference between HashMap and TreeMap in Java?

18. What is multithreading in Java?

19. What is synchronization in Java?

20. What is a deadlock in Java?

Interview Questions for Experienced Java Developers

Below we've bifurcated interview questions and answers for Java programming based on years of experience.

Java Developer Interview Questions for Developers with 5+ Years of Experience

21. What is the difference between volatile and transient variables in Java?

22. What is the difference between Vector and ArrayList collections in Java?

23. Can you write a code representing thread-safe singleton patterns in Java?

24. What is the difference between hashCode and equals in Java?

25. A colleague with lesser Java experience is having a hard time serializing class. How would you help?

26. What will the expression 1.0/0.0 return in Java?

27. How is creating a string with a new operator different from a literal one?

28. Why are strings made immutable in Java?

29. What is a ternary operator in Java? Can you give a few examples of where they are used?

30. Can you explain the concept of a catch block?

31. What are the options for capturing thread dumps in Java?

32. How is thread context switching done in Java? Can you explain with an example?

33. How to call the wait method in Java? Do you use an if block or a loop?

34. Are you familiar with the latest Java release?

35. How would you explain a wrapper class to a Java student?

36. Can you explain the difference between path and classpath variables in Java's architecture?

37. What is a JIT compiler in Java?

38. Explain the term 'late binding' in Java.

39. What is the dynamic method dispatch in Java?

40. What is the difference between >> and >>> operators in Java?

41. Explain the life cycle of Java Applet.

42. What are daemon and non-daemon threads in Java?

43. What is Java enumeration? Can you give examples?

Java Developer Interview Questions for Candidates with 10+ Years of Experience

44. What is a singleton class in Java? How to implement a singleton class?

45. Can you differentiate between a String, StringBuffer, and a StringBuilder?

46. What is a Java comparator? How to use a comparator in Java?

47. Can we override a private or static method in Java? Explain.

48. How is a HashSet different from TreeSet in Java?

49. What is a reflection in Java? Why is it important?

50. Describe the life cycle of a thread in Java.

51. Can you explain the different ways of thread usage in Java?

52. What is the default priority of a thread assigned by JVM? What are the other thread priorities in Java?

53. What do you understand by object cloning? How do you achieve it in Java?

54. What is exception propagation, and how will you execute it?

55. What happens if an exception is not handled in the Java program?

56. Can you call a constructor inside another constructor in Java? How?

57. Can you explain why the Java array index starts with 0 instead of 1?

58. Is deletion faster in an array or linked list? Can you explain the reason?

59. How is the ArrayList internally implemented in Java?

60. What is aggregation and composition in Java?

61. Is composition more advantageous than inheritance in OOP? Why?

62. How are the 'new' operator and 'newInstance' operator different in Java?

63. Is it possible to import the same class/packages two times in Java?

64. What is the marker interface in Java, and why is it required?

65. What is 'Double Brace Initialization' in Java?

66. When will an object be eligible for garbage collection in Java?

67. What is a memory leak in Java? How can you detect it?

68. What is dependency injection, and when should you use it?

69. What is the difference between default and protected access specifiers?

70. Why are generics used in Java programming?

Interview Questions for Java Developer Freshers

Here's a list of questions to ask Java Developer freshers:

71. Is Java a pure object-oriented language? Why or why not?

72. What are the similarities and differences between Java and C++?

73. What are the main features of Java programming language?

74. What is the difference between a program and a process in Java?

75. What is the difference between an inner class and a sub-class?

76. What purpose do static methods and static variables serve?

77. What is the difference between double and float variables in Java?

78. What are loops in Java? Name the three different types of loops.

79. What are Java packages? What is their significance?

80. Does Java support using pointers? Why or why not?

81. What do you understand by local variable and instance variable?

82. What are the default values assigned to variables and instances in Java?

83. What do you mean by infinite loop? Give an example.

84. What is the difference between the continue and break statement?

85. Are you familiar with the concept of constructor overloading? Explain it briefly.

86. Why is the main method always static in Java?

87. What are shallow copy and deep copy in Java?

88. What are the memory allocations available in Java?

89. What is the difference between Stach and Heap memory in Java?

90. What is an association in Java?

91. What is copy constructor in Java?

92. Explain Java String Pool.

93. What is the final keyword in Java?

94. Can we have a try block without a catch block in Java?

95. What is the purpose of using a break statement in a switch statement?

Tips for Interviewing Java Developers

The marketplace for Java developers is huge, with many talented developers. Knowing how to interview them can help you find the best match for your company. Here are some interview tips for selecting the right candidates:

1. Test Their Java Version Knowledge

Besides interview questions and answers for Java, hiring managers should ensure that candidates are familiar with the Java version the company is using.

Most candidates list the Java version they've used in their CVs. But if they don't, bring up the topic in the interview.

2. Assess Their Soft Skills

Apart from technical skills, soft skills such as communication, problem-solving, and teamwork are also important in a Java developer. An interviewer should assess these skills by asking behavioral questions.

Most hiring managers ask similar open-ended questions to all candidates and compare their responses. Here are some examples:

• What was the most significant problem you solved in your last workplace?
• Describe the time you faced a challenge in your workplace. How did you overcome it?
• What do you do if your team members disagree with your decision?
• What is your best and worst quality?
  

The best route is to conduct a Java test when checking knowledge of Java tools, methodologies, software, and programming language.

It will effectively filter skilled developers, so the HR team won't waste time interviewing unsuitable candidates.

Recruiters can consider including the following tests in their hiring process:

• Java Coding Test
• Core Java Online Test

Wrapping Up

In order to gauge the technical and non-technical skills of Java developers, the hiring team can utilize iMcoha's online Java test to filter out top candidates and reduce their load.

With iMocha, recruiters can objectively assess a candidate's Java programming skills and reduce technical screening time by 85%.

FAQs

1. What does a Java developer do?

The core responsibility of a Java developer is to develop applications, software, and websites for businesses using the Java programming language.

2. What are the basic Java developer skills?

The essential skills required to be a Java developer are:

• Object-oriented programming concepts (OOP)
• System design and architecture
• JVM internals
• Java build tools
• Web technologies
• Code version control
• Java testing tools
• Core Java skills

3. What soft skills are required for a Java developer?

Apart from core Java skills, developers must have soft skills such as communication, teamwork, and problem-solving.

4. What are Java full-stack developer skills?

A full-stack Java developer should have the skill to develop both client software and server software. They should be well-versed with frontend and backend technology, development languages, version control system, and APIs.