Top 30 Java Interview Questions and Answers in 2022
  • Cyber Success
  • February 18, 2022
  • Java

Top 30 Java Interview Questions and Answers in 2023.

Java is a first choice amongst many businesses so if you want to set your career as a java programmer the competition is very much high. But mastering Java is not an impossible task, it just demands some level of determination and dedication.

No matter if you are a fresher or experienced person, when you want to move forward in your career you need to face an interview. Here we will make your interview experience better and will help you to get completely ready for the interview, with some very helpful java questions and answers.

Java Interview questions and answers in 2023

For better understanding we are going to differentiate questions and answers for Freshers and experienced ones.

Java Interview questions and answers for freshers:

Q1. What is Java?

Java is an object oriented general purpose programming language. It can be used to develop websites, applications and games. Java is the most liked programming language in the world. It was developed by sun microsystems.

Q2. Why is java a platform independent language?

It is called so because it can run on any operating system Because of its byte codes. We don’t need any modification; a single program can run on different platforms.

Q3. What is the difference between Java and C++?

  • C++ supports both procedural and object oriented while java is object oriented language.
  • C++ is platform dependent language while java is platform independent
  • Memory management in C++ is manual while in java memory management is system controlled
  • Global and namespace scopes are supported in C++ while java does not support global scope

Q4. Why is java not a 100% pure object oriented language?

Java is not a pure object oriented language because it uses 8 types of primitive data such as Char, byte, boolean, short, int, float, long and double.

Q5. What is meant by JVM?

JVM is nothing but Java virtual machines. JVM accepts and executes bytecode, basically it works as an interpreter.

Q6. What are the features of Java?

As Java is easy to learn it is considered as an easy programming language. Java is platform independent, object oriented, multi threaded, and interpreted.

Q7. What is the meaning of “object” in Java?

A java object is an instance or a member of a class which has an unique identity, state and also behavior. Class acts as a template from which objects are created.

Q.8 Define “Class” in Java?

A class acts as a template from which objects are created. There are methods and fields in the class from which the nature of an object is defined.

Q.9 List down some keywords of Java?

Below are some keywords of java:

  • Boolean
  • Abstract
  • Byte
  • Break
  • Switch
  • Class
  • Catch

Q10. List some IDE’s of Java?

IDE is nothing but an integrated development environment. Below are some IDE’s of Java:

  • Eclipse
  • Netbeans
  • BlueJ
  • Jcreator
  • jEdit

Q11. There is default value for byte datatype in Java, what is that value?

In Java programming language 0 is the default value of byte data type.

Q.12 What are the default values of double and float data types in Java?

0.0d is the default value of the double data type in the Java programming language.
0.0f is the default value of float datatype in Java programming language.

Q.13 What is meant by an exception in Java?

An exception is an event in Java programming language, which occurs during the execution of a program, that breaks the normal flow of the program’s instruction.

Q14. Which three classes java.util.regex contains?

Below are the classes:

  • Pattern class
  • Matcher class
  • PatternSyntaxException class

Q15. When can we use the parseInt() method in Java?

parseInt() method is used in Java programming language to get the primitive data type of a certain string.

Java Interview Questions experienced with Answers:

Here we are going through some advanced Java interview questions.

Top Java interview questions:

Q16. How can we achieve encapsulation in Java?

There are two ways to achieve encapsulation in Java

  • First one is by stating the variables of a class as private
  • While changing and viewing variables values offer getter method and public setter

Q17. What is the life cycle of servlets?

There are five stages in the servlet life cycle:

  • The Servlet is destroyed
  • The servlet is initialized
  • The servlet is loaded
  • Service the request
  • The servlet is instantiated

Q18. What is JDK in Java? What are the variants of JDK?

JDK is nothing but Java development kit. Basically it is a main technology package used in the Java programming language. It is used for developing java based applications as it offers a collection of tools and libraries necessary for development.

Below are the variants:

  • Java development kit (JDK) Standard Edition
  • Java development kit (JDK) Enterprise Edition
  • Java development kit (JDK) Micro Edition

Q19. What is a JIT compiler in Java?

JIT compiler stands for Just in Time compiler. It is enabled by default and it gets activated whenever a java method is called. It can improve the performance of Java applications as it compiles platform neutral Java bytecode into native machine code at the runtime.

Q20. What difference is there between JDK, JRE and JVM?

  • JDK works as a software development kit
  • JDK is used to write Java programs as it has tools required to write
  • JRE is basically used to run Java programs as it has software bundle which allow Java program to run
  • JRE don’t have any tool which supports java development for eg. compiler or debugger
  • JVM acts as an environment for purpose of executing bytecode
  • JVM contains just in time compiler tool so it runs faster than other applications

Q21. How is garbage collection executed in java?

When in java any particular object is not referenced, garbage collection is executed and the object gets destroyed automatically. Java calls System.gc() or Runtime.gc() methods for the sake of automatic garbage collection.

Q22. In Java can we execute any code even before the main method?

Yes it is possible, for that we can use the static block of code from a class. Statements from this static block of code can get executed once at a time of loading the class even before creation of the object in the main method.

Q23. What do you know about multi-threading?

Even though explicit constructor is not defined in Java, default constructor is used for object creation so objects get created effectively. This constructor doesn’t have any parameters.

Q24. Do you know any examples of using pointers in Java class?

There are no concept pointers in the Java programming language.

Q25. How to use goto in Java to go to a specific line?

In Java we can not go to any particular line tagged. And there is no such a keyword like goto in Java.

Q26. In Java How to start a thread which is in dead state?

In Java, there is no chance to start a dead thread as there is no such an option available.

Q27. In Java if i want to preserve data of an object for the purpose of later use. What is the better approach to use?

Using the concept of serialization is a better way to persist data for future use.
In multi-threading multiple tasks run simultaneously in a single program. Multi-threading helps to improve performance significantly. Threads run in a parallel manner within the same process stack.

Q28. What is the use of Runnable Interface in Java?

The significance of a runnable interface in java is it allows implementation of multi-threaded applications. Java.Lang.Runnable is an interface It is implemented by class to allow multi-threading.

Q.29 Why do we use Break in each case of switch statements?

Break is used after every valid case so as to break the code so that it doesn’t flow into progressing cases too.

Q30. What is meant by Abstraction in Java programming language?

Abstraction is used in Java to hide internal working from an user while the user can easily access external functionalities. The user doesn’t know how functions are working internally and still the user can access its functions.

Related Readings:

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Recommended Reading – Career Opportunities in Java in India