Java Interview Questions

Introduction

Java is both a platform and a programming language. It is an object-oriented, high-level, and secure programming language. Since java has its runtime environment (JRE) and API, it is called a platform.

Java is used in the development of

  • Desktop applications such as media players, antivirus, etc.
  • Enterprise Applications such as banking applications.
  • Mobile
  • Robotics
  • Games, etc.

The key advantages of learning Java Programming:

  • Object-Oriented
  • Platform Independent
  • Simple
  • Secure
  • Portable
  • Robust

This article will see all types of Interview Questions related to Java Programming language.

So, let’s get started with the Interview Questions.

Basic Level Interview Questions

  1. What is Java?
  2. Compare and contrast C++ and Java?
  3. List some of the features of the Java Programming language?
  4. What do you know about Java Virtual Machine?
  5. Compare JDK, JRE, and JVM?
  6. Name the various types of memory areas allocated by JVM?
  7. What is a JIT compiler?
  8. Explain platform?
  9. How will you compare the Java platform and other platforms?
  10. Does Java have a feature of ‘Write once and run anywhere? Explain how?
  11. Define classloader?
  12. What happens if I write static public void instead of the public static void?
  13. Mention the default value of the local variables in Java?
  14. Tell me about various access specifiers in Java?
  15. What is the main purpose of static methods and variables?
  16. List some advantages of Packages in Java?
  17. Explain the ‘Object-Oriented’ paradigm?
  18. Explain Object?
  19. How will you differentiate object-oriented programming language and object-based programming language?
  20. Define Constructor?
  21. Name the types of constructors used in Java?
  22. What is the main aim of the default constructor?
  23. Can we inherit the constructor?
  24. Explain copy constructor in java?
  25. Differentiate between Constructors and methods?
  26. What do you know about static variables?
  27. What is the static method?
  28. The main method is static? Why?
  29. Is there any way to override the static methods?
  30. What is a static block?
  31. Is it possible to execute a program without java’s main () method?
  32. Write differences between the static (class) method and instance method?
  33. Is it possible to make constructors static?
  34. Can we make abstract methods static in java?
  35. List some uses of the ‘this’ keyword?
  36. Explain Inheritance?
  37. What is the use of Inheritance in Java?
  38. Name the class which is a superclass for all the classes?
  39. What is the main reason that java does not support multiple inheritances?
  40. Differentiate between aggregation and composition?
  41. Does java support pointers? If not, why?
  42. What is super in java?
  43. What are the important uses of the super keyword?
  44. Compare this and the super keyword?
  45. What do you know about object cloning?
  46. What is method overloading?
  47. Explain method overloading with type promotion?
  48. Explain covariant return type?
  49. What are the final variables?
  50. What is the final blank variable?
  51. Does the Java language support method overload by changing the return type?
  52. Is it possible to overload the methods by making them static?
  53. Is overriding the overload method possible?
  54. Can we manipulate the scope of the overridden method in the subclass?
  55. Highlight some differences between the final method and abstract method?
  56. How java is different from javascript?
  57. Which language is better, according to you – java or python?
  58. Explain String pool in java?
  59. What do you know about the interface in java?
  60. Explain thread lifecycle in java?

Advance level Interview Questions

  1. Why java is not a complete object-oriented language?
  2. Explain the default and parameterized constructors in java?
  3. For how long does heap and stack memory live in java?
  4. What is an instance variable in java?
  5. Differentiate between instance variable and local variable in java?
  6. What is the meaning of ‘final’ with context to method?
  7. Define “final class” in java?
  8. What is the role of JIT?
  9. Compare and contrast an object and a class?
  10. Explain the advantages and disadvantages of java sockets?
  11. Explain garbage collection in java? What is its use?
  12. Explain synchronization concerning multithreading?
  13. Mention the different ways of using threads?
  14. Explain Immutable class? How can we create immutable classes?
  15. Explain pass by value and pass by reference in terms of Java?
  16. Differentiate between Array list and vector?
  17. What are Hashmap and Map?
  18. What is an iterator?
  19. Write one line of code that represents an array that is not null but empty?
  20. Is it possible to have multiple main methods in the same class?

Core Java Interview Questions

  1. Is there any need to import java.lang package anytime?
  2. Can a user import the same package/class twice?
  3. Can JVM load the package twice at runtime?
  4. What do you understand by checked and unchecked Exception?
  5. Explain different types of inner classes?
  6.  At compile time in Java, are the imports checked for validity?
  7. When we import a package, do the sub-packages also get imported as well?
  8. Explain the difference between declaring and defining a variable?
  9. Mention the default value of an object reference declared as an instance variable?
  10. A top-level class is private or protected?
  11. Define Serialization?
  12. How can we serialize an object to a file?
  13. Differentiate between compile time and run time polymorphism?
  14. Explain Encapsulation in java?
  15. What are literals?
  16. Is the code written below valid or not?
    short s=10;
    s=s+10;
  17. Explain the two-dimensional array?
  18. Highlight differences between the add and offer methods on the Queue interface?
  19. How will you swap two elements in a list?
  20. What are the different ways to handle exceptions in java?

 

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