Popular 2023 Java Interview Questions

With Java being one of the most ubiquitous programming languages, aspiring developers should obtain fundamental knowledge of it. In this article, we have compiled a set of commonly asked Java interview questions designed to aid recruiters in appraising a candidate’s expertise. Additionally, we present a brief account detailing the history of Java and its distinct features.

A Brief Overview of Java’s Evolution and Key Milestones

Java follows the Write Once Read Anywhere (WORA) approach, making it a sophisticated high-level, object-oriented, class-based language. This exceptional feature allows Java-generated code to run on any environment that supports the Java Runtime Environment (JRE) without modifications, with minimal implementation necessities. This is possible due to the ability of Java Virtual Machines (JVMs) to execute bytecode produced during the Java compilation process, ensuring application independence from computer architecture.

Java’s syntax is similar to that of C and C++, which simplifies the learning process for proficient programmers. The language has garnered immense popularity due to its broad array of features and exceptional collection of libraries and frameworks.

Java was initially developed in 1991 to be employed in interactive TV sets, although the technology was inadequate for this purpose at the time. However, it was released in 1996 and has since gained immense popularity, primarily due to its WORA functionality and familiar syntax. Consequently, it has established a substantial following among software developers who appreciate the language’s network and file access control as well as its adjustable security features.

The historical landmarks of Java’s evolution can furnish an excellent subject matter for interview questions. For example, in 1997 the standardization of JVM was initiated, and almost the entire source code of JVM was disclosed as open-source software in 2006. Also, throughout these years, earlier versions were gradually phased out. Though insignificant at first glance, such information could be valuable while dealing with legacy code.

Sample Interview Questions to Acquire Java Skills

By referring to “basic Java interview questions,” we imply questions that are appropriate for university interns or entry-level developers with little or no experience. These Java interview queries are developed to appraise a candidate’s Java comprehension. Usually, individuals posed with such interview questions will have studied Java in an academic setting rather than a professional context. Depending on the Java interviewee’s responses, supplementary training may be required; hence such inquiries frequently embrace both simple and advanced subjects.

1. Kindly furnish a summary of Java’s fundamental concepts.

For someone new to Java, this is frequently the first question asked during an interview. Though there are ample online resources providing descriptions of various Java components, the response to this inquiry transcends mere technical competence and is often the foundation for deciding to adopt the programming language.

2. Contrast Java with another programming language, such as C++ or C, and elucidate the dissimilarities.

This question frequently arises during Java programming interviews; hence anyone venturing into the Java programming field should be well-acquainted with the answer. It is critical to consider platform requisites, features such as inheritance, overloading, calling and overriding when addressing the question. Furthermore, understanding the programming language’s objectives, language, and applications is also significant.

3. Characterize the key characteristics and abilities of Java.

This Java interview inquiry has great adaptability because of the wide-ranging topics it can incorporate, such as primitive data types, abstraction, and encapsulation. Each of these ideas could be further delved into with separate interview questions.

4. Provide a Definition of Bytecode in Java

Java’s catchphrase of “write once, run anywhere” is facilitated by bytecode. Java programs are compiled by the Java compiler into platform-neutral bytecode, which serves as a connector between the primary source code and machine code.

5. Elucidate what a Java Virtual Machine (JVM), JRE, and JDK (Java Development Kit) are and differentiate between them.

It is apparent that the responses to the given Java interview queries are closely entwined, with numerous shared features serving as both defining and discerning factors. For instance, a likely example could be…

  1. The term “Java Virtual Machine” pertains to the theoretical machine that generates the requisite circumstances for executing Java programs.
  2. The Java Runtime Environment (JRE) is the concrete manifestation of the Java Virtual Machine (JVM), furnishing the essential software tools for creating Java applications.
  3. The Java SE, ME, and EE implementations utilize the same Java Runtime Environment (JRE) and roster of development tools.

6. Built-in Data Types of Java

One of the most essential yet intricate Java interview inquiries is: how can the data type of an object be modified? This is a complicated subject since the eight primary data types have specific definitions and restricted ranges, despite being mirrored in various programming languages. This can create confusion for those not well-versed in a language and its inbuilt data types. This subject intersects with the one regarding the features of Java, so you may field questions on this issue.

7. Explain the Garbage Collection Process

Although it may be a routine component of Java programming, the garbage collection process may be presented in isolation in certain interviews. As a result, it has been added here specifically.

8. Elucidate the JIT Compiler and its Functioning in Java.

The dedicated compiler creates numerous modules of bytecode that carry out related operations in parallel. This is a popular topic in Java interviews due to its capacity to expedite the compilation process and enhance performance.

9. Defining the Term “Classloader” and Elucidating the Different Classloader Configurations

The Java Virtual Machine (JVM) has a classloader subsystem responsible for loading class files. This code is carried out when the program is initially launched. The classloaders are classified into three categories: bootstrap, extension, and system/application.

10. Overview of the Different Class Specifiers and their Usage

Class specifiers, or Java’s keywords, are employed to define the extent of a function, class, or variable. As this is a widespread topic in Java programming, it is frequently examined in interviews. There are four distinct types of access specifiers, each with its own meaning. These are frequently discussed in Java interviews.

High-Level Questions for Java Interviews

1. Defining, Comparing, and Describing the Usage of Java Characteristics such as Polymorphism, Inheritance, and Encapsulation.

While the significance of Java’s characteristics has been covered earlier, particular attention must be given to the ones described here since they are vital to the functioning of numerous languages and define their essence. As a result, they are frequently included in programming interviews for languages such as Java. Additionally, the implementation may vary between languages, with Java interviews usually concentrating on the language’s unique implementation.

2. Elucidating Java’s Constructors and the Concept of Constructor Overloading.

Java interviews usually concentrate on how to become a Java developer. Queries may pertain to subjects such as object memory allocation and initialization, distinctions between default and parameter constructors, and skills like returning values, overloading, and creating static variables.

3. Exploring the “this” Keyword in the Java Language

Java interviews frequently include inquiries about the ‘this’ keyword, which acts as a reference to the pertinent object that a variable is currently pointing to. These questions can differ in complexity, ranging from general queries about the theme to more particular questions about a particular scenario or topic.

Moreover, to evaluate the proficiency of an individual in Java, it is advisable to ask more detailed questions. Having a thorough understanding of the concepts pertaining to Java is essential, not just practical knowledge, and the ‘this’ keyword can serve as a shortcut to achieving such understanding. For instance:

4. Is It Possible to Save a File with the .java Extension in Java?

When dealing with advanced Java interviews, it is crucial to keep in mind other factors, such as the capability to execute by Java classname, despite the queries not being overly intricate.

5. Can Code be Executed in Java Before the Main Function is Invoked?

It is established that in Java, the static initializer block is executed before the main function. This subject is frequently addressed in Java programming interviews, especially regarding the feasibility of running a program without the main method.

6. A Java Application Can Operate Without the main() Method.

This is feasible only in cases where the static block is utilised, but only with JDK versions before 1.7.

7. Can a Value be Set for this Variable?


8. Can You Predict the Result of the Java Program?

This Java interview question is quite extensive and can be worded in various ways. The query may involve predicting the output of a program, even if its syntax is confusing, determining whether a program can operate, assessing reported errors and identifying how to address them.

Queries for an EE Java Interview

J2EE denotes Java 2 Enterprise Edition and is applied in creating and implementing enterprise applications in multiple languages. Given its extensive adoption in business, we have incorporated a FAQ section to provide answers to some of the most common questions about J2EE.

Explain J2EE

This aligns with the Java programming interview questions discussed earlier. The explanation should encompass not only the full name and its significance but also its principal operations and attributes.

Define the J2EE Add-On and Outline its Functionality. What are the Different Types of J2EE Modules, and How do they Operate?

A J2EE module comprises one or more container type J2EE components. During a Java interview, questions may surpass the fundamentals of the language and investigate particular themes relating to various subsets, along with their definitions.

The Struts Framework in J2EE

Struts is an application development framework based on the Model-View-Controller (MVC) paradigm that holds substantial importance in development. Hence, Struts and related components are frequently addressed in Java interview questions, particularly in Enterprise Edition (EE).

Hibernate in J2EE

Hibernate is a query and object service that augments the expressiveness of SQL. In this segment, we will investigate explanations of Hibernate and HQL, its uses, benefits, and drawbacks, along with the procedures required to integrate Hibernate mapping files and file extensions for mapping and configuring, all of which are core to J2EE.

The New Phase of J2EE

Spring is a lightweight open-source application development framework for enterprises, similar to Struts. Like Struts, the framework’s modules have various potential topics to be explored, such as their meanings and applications.

What Other Topics Should I be Ready to Discuss Aside from Standard Java Programming Interview Questions?

In addition to the aforementioned inquiries, the relevance of theoretical Java interview questions decreases when recruiting for more senior roles. Senior candidates should possess the required knowledge and expertise to offer insight on intricate and unforeseeable matters while also being able to mentor junior staff on programming intricacies. This is because senior hires are anticipated to have experience in these areas from prior positions, or because they may be responsible for tasks like leading teams, testing products, and managing clients.

In Java position interviews, it is recommended to emphasize a candidate’s practical experience over their theoretical knowledge. To facilitate this, here are some interview questions you could consider asking:

  1. How much experience do you have with Java programming?
  2. How many distinct frameworks, packages, and libraries related to Java have you utilised?
  3. What measures did you take in addressing the challenges that surfaced in your assignments?
  4. How well-versed are you with programming environments and languages related to Java?

Candidates should anticipate being asked about their proficiency not only in Java but also in other technologies.


The mentioned Java interview questions are simply a subset of numerous questions that may be posed. You can locate further Java-related interview questions on different websites and blogs. Additionally, various Java libraries and frameworks should be taken into account as well. It should be kept in mind that simply memorising these questions is not as advantageous as having a comprehensive comprehension of the subject matter along with the application experience as outlined in the previous section.

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