Sun, 28 Nov 2021

Whether you are among the experienced Java developers or programmers who are just out of college looking to start their career, you all will face the same challenge of passing the technical interviews. Some companies use these challenges to test your skill set to check your expertise in the tech stack you will use daily. On the other hand, some companies use these challenges as a practical assessment of your past experience that you will use in the new role.

There is no doubt that Java is the most widely used programming language in the current IT world. One of the key reasons for many Java developers in the programming field is the career potential that comes with understanding and using Java. So, if you want to crack Java interviews, this article is for you. Below, we have compiled a list of the most frequently asked Java Interview questions that a Java programmer must know.

Top 15 most frequently asked Java interview questions

It is impossible to land a job by just submitting a detailed Java developer CV. Additionally, you need to pass the technical interview. Here is the list of a few Java interview questions -

  • What is Java?

This is the fundamental question that all Java developers have been asked at one point in their career.

Java is a high-level, general-purpose, class-based, object-oriented, and secure programming language. It is the most popular development platform that accelerates projects and supports a wide range of emerging technologies.

  • What are JDK, JRE, and JVM? Explain the difference between them.

JDK, JRE, and JVM are the concepts you will encounter when you install the software. Hence, it is one of the essential topics that Java developers should understand and know.

JDK - It stands for Java Development Kit.

JRE - It stands for Java Runtime Environment.

JVM - It stands for Java Virtual Machine.

It is a software development kit dedicated solely to software development.It is a set of resources and libraries required by Java programs to run.It is a runtime environment used to execute bytecodes.
JDK is platform-independent.JRE is also platform-independent.Whereas, JVM is not platform-independent.
It contains tools for developing and debugging.This contains supports files and libraries.JVM does not comprise any software development tools.
It comes with an installer.It has a runtime environment to execute source code.Whereas it is bundled in both JDK and JRE.

  • What is a ClassLoader in Java?

It is a part of the Java Runtime Environment that is used to load class files. Whenever Java developers execute a program, it is loaded first by the ClassLoader. Java has three built-in ClassLoaders, they are -

  1. Bootstrap ClassLoader
  2. Extension ClassLoader
  3. Application ClassLoader

  • What is memory allocation in Java?

Memory allocation is a process that allows Java developers to set aside virtual memory sections to store variables and instances of structure and classes. Five significant types of memory allocation in Java are -

  1. Class memory
  2. Heap memory
  3. Stack memory
  4. Program counter-memory
  5. Native method stack memory

  • What is a thread in Java?

Thread is a path that is followed when a program is executed. They are independent smallest units of processing that can perform complicated tasks in the background without interrupting the main program. It is one of the key concepts in Java. This is why before appearing for any interview, Java developers should be clear with Java threads.

  • What are Java developer roles and responsibilities?

A Java certified programmer's responsibilities include -

  • Designing, developing, and maintaining Java-based applications.
  • Writing readable, clean, testable, scalable, and efficient code.
  • Testing and debugging newly developed applications and recently added updates.
  • Maintaining reports and documentation.
  • Contributing to all phases of the software development life cycle (SDLC).
  • What are the skills required for Java developers?

The top eight Java developer skills that programmers are required to master -

  • Core Java
  • Relational Databases and Object Relational Mapping (ORM)
  • Java Build Tools
  • Java Web Frameworks
  • Application Containers
  • Java Testing Tools
  • Big Data
  • Java EE Components
  • What is inheritance in Java?

It is a concept that acquires properties and functionalities from one class to another. The goal here is to provide reusability to Java developers. They only have to write unique features and extend the common ones from another class. The class that inherits the features from another class is called the child class. The class whose features are inherited by other classes is called parent class (also called super class or base class).

  • What is enumeration in Java?

It is a list of named constants that defines a class type. Created using the enum keyword, it can have constructors, methods, and instance variables. The main objective of enumeration is to allow Java developers to define their own data types, that is, enumerated data types.

  • What is abstraction in Java?

We already know that objects are building blocks of Java, and each object contains some features and properties. Abstraction allows Java developers to 'display' only the relevant features and 'hide' the unnecessary details from the outside world.

  • What is encapsulation in Java?

It is another important question that is frequently asked to Java developers. It is a process that secures the data (variables) and the code manipulating the data (methods) in a single unit.

  • What is a collection in Java?

It is a set of individual objects that are grouped as a single unit. It is used by Java developers to perform functions like - searching, sorting, insertion, manipulation, and deletion.

  • What is Java API?

This is another important question that Java developers should be aware of. APIs in Java are used to integrate various applications and websites to offer real-time data.

  • What is static in Java and its use?

It is a keyword used for memory management and can be utilized with variables, methods, blocks, and nested classes. It is used for constant variables or methods that are the same for every instance of a class.

  • What is a Java package?

A package in Java is used to group similar types of classes, interfaces, and sub-packages. It can be categorized into - built-in packages and user-defined packages.


It is crucial for Java developers to go through questions that can be asked in the interview process. It is the best way to get you on the safer side as it prepares you to be able to answer the questions that interviewers might ask. So before appearing for any interview, make sure you understand all the concepts or questions mentioned above.

Author Bio -

Anupriya Singh

Anupriya is a content writer who is passionate about writing on a variety of topics. When not writing, you can find her reading or sketching.

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