Java Interview Questions for Beginners & Advanced

Often while we talk about the software development domain, mention of java comes up in discussion. It is one of the most important contributors in the domain, so talking about it is quite common. Just knowing about it or having the theoretical knowledge of java is not enough if you do not use it in real-time. However, if you are a beginner, the Java interview questions and answers you should be preparing may include the following:

What is Java?

One of the most important Java interview questions is what Java is. This is a vital question as the interviewer would like to know if you have a basic understanding of Java.

Released in 1995 by Sun Microsystems, Java is an object-oriented programming language as well as a computing platform.

Why is Java used?

Java is mainly used to create complete applications which can run on a single system or can also be distributed to several servers as well as clients in the network. This means Java Certification in Manila can be used to build mobile applications as well as those designed to run desktop applications. Also, it runs on various operating systems and servers.

How to install Java?

Java can be installed in a few simple steps:

  • Visit and click on the button of Free Java Download
  • Now click on the Save button to save the software on your desktop
  • Once you verify that the software is saved on the desktop, you can Windows Command Prompt window

For Windows XP: Click Start -> Run -> Type: cmd

For Windows 7 and Windows Vista: Click Start -> Type: cmd in the Start Search field.

cd <Java download directory>

Now, at last, run the installer and follow all the instructions you get on screen.

How to reverse string in Java?

String in Java can be reversed in many ways. You can use StringBuilder, StringBuffer, iteration, etc. to reverse the string.

public class StringFormatter {

public static String reverseString(String str){

StringBuilder sb=new StringBuilder(str);


return sb.toString();

What is thread in Java?

Thread in Java enables a program to operate effectively by doing several things at one time. Threads are used to perform difficult tasks in the background while keeping the main program free from any interruptions.

What are the memory areas allocated by Java Virtual Machine?

  • Classloader
  • Class area
  • Heap
  • Stack
  • Program Counter Register
  • Native Method Stack

Is Java platform independent? 

Yes, Java platform is independent. Java code can be written on one platform and you can run it on another platform. Taking as an example, the code can be written and compiled on windows while you can run the generated bytecode on any other supported platform which can even be Linux.

Java vs. C ++?

Considered as one of the Java interview questions for experienced programmers, this question helps you showcase your Java knowledge and also how much you know about the C++ programming language.

  • Starting with platform dependency; Java is platform independent while C ++ is platform dependent
  • About goto support; Java does not provide support to goto statement, while C++ supports goto statement
  • For multiples inheritance; Java does not support multiple inheritances but C++ does
  • For multithreading; Java supports multithreading, C++  lacks in-build thread support
  • Talking about the virtual keyword; Java has no virtual keyword but C++ has it.

What is Javac?

Javac is a compiler that produces Java bytecode from the source code. The bytecode is executed by JVM to run the program.

What is a wrapper class in Java?

A wrapper class changes the primitive data type which includes byte, int, char, and boolean, to name a few to the objects of their classes in particular like Byte, Integer, Character, Boolean, etc.

What is a path and classPath in Java?

Path indicates the .exe files location, while classPath indicates bytecode location.

What are the various data types in Java?

  • byte – 8 bit
  • short – 16 bit
  • char – 16 bit Unicode
  • float – 32 bit (real number)
  • int – 32 bit (whole number)
  • long – 64 bit (Single precision)
  • double – 64 bit (double precision)

What is Unicode?

Unicode means a totally international character set that denotes all the characters that are found in human languages. You can say Unicode is used for representing the characters.

What are Literals in Java?

Literal in Java is the constant value that has been assigned to a variable.

What is a break statement?

Break statement in Java is used for breaking the flow sequence. It is mostly used along with switch case data structure as it helps in coming out of the statement as a case is executed. You can use a break statement to come out of the loop.

These questions are helpful to get you familiarized with the fundamentals, which can be helpful not only for an interview but also to evaluate yourself while learning Java. For more great questions about Java and other programming languages, you can visit the Great Learning Academy website.