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Java Developer Interview Questions

Last Updated on:

27 February 2023
Java Developer Interview Questions

A programmer that creates, develops, and maintains applications and software that are based on the Java platform is known as a Java developer. Because most large companies use Java to construct software solutions and backend services, becoming a Java developer is currently one of the jobs in the highest demand.

Continue reading to learn about essential topics, such as -

  • The tasks and responsibilities of a Java developer. 
  • The skills necessary to become a Java developer. 
  • The average compensation for a Java developer. 
  • Java developer interview questions, how to ace them, and much more!

What Does a Java Developer Do?

The creation of programs and software through the use of  Java falls under the purview of a Java developer. A Java developer works in conjunction with developers and engineers in order to incorporate Java. Because Java is still one of the most widely used programming languages today, software engineers proficient in Java are in high demand. 

This programming language is utilized by a variety of significant organizations to create and maintain their internationally recognized products.  

They are included in the software development process at every stage of the software's life cycle. They have to be able to recognize and assess any concerns or problems and then think of practical solutions to those issues or problems. Other responsibilities may include compiling and recording user needs, conducting data analysis, and testing for QA.

During the course of the software development, a developer is accountable for a variety of Java-related responsibilities, ranging from conceptualization and planning to execution. The developer is tasked with developing user data services, which must be accomplished through the design, implementation, and regular maintenance of Java-based aspects and integrations.

Here are some job responsibilities of a Java developer.

  • Assist in seeking out new options and methods, providing for architectural evaluation, and continual improvement.
  • Analyze user needs to establish company goals.
  • Create and evaluate programs.
  • Create technical blueprints for the creation of applications.
  • Create multimedia programs.
  • Control the creation of Java and Java EE applications.
  • Create materials to assist users.
  • Find and fix any emerging technical problems.
  • Imagining key capabilities and attributes.
  • Make sure application designs adhere to corporate objectives.
  • Making specifications out of necessities.
  • Make comprehensive design specifications.
  • Plan and create system and software deployments.
  • Redesign the architecture of Java as it is currently.
  • Write robust and dynamic code.
  • Understand the goals and the application's capabilities.

Basic Skills Needed for a Java Developer Job

Here are examples of skills and competencies a Java developer is expected to have and perform:

  • Java expertise, along with a solid comprehension of the ecosystems supported by it.
  • A solid understanding of the patterns and concepts used in object-oriented programming (OOP).
  • Working knowledge of a variety of design and construction patterns.
  • The ability to write Java libraries that can be reused.
  • Familiarity with the concurrency patterns used in Java.
  • History of successful collaboration with well-known web application frameworks such as Play and Spark.
  • Knowledge of relevant Java GUI frameworks, such as Swing, SWT, and AWT, in accordance with the requirements of the project.
  • Capability to write Java code that is organized and easy to understand.
  • Knowledge of the fundamentals of the Java class loading process.
  • Familiarity with working with both external and internal databases.
  • Acquiring an understanding of the fundamental design ideas that underpin a scalable application.
  • Capable of developing database schemas that accurately characterize and provide support for business activities.
  • A fundamental understanding of the Java Virtual Machine (JVM), including its faults, vulnerabilities, and potential workarounds.
  • Putting in place highly autonomous assessment tools and individual tests.
  • A comprehensive understanding of code versioning systems, such as Git is required.

Educational Qualifications

Employers usually look for individuals with the following:

  • Bachelor's Degree in Computer Science or a relevant field
  • Master's Degree in Computer Science or a relevant field

You can enroll in an online Java development course even if you lack a foundation in computer science yet desire to build Java applications. There are a few online diploma programs in programming that offer Java programming classes, but these programs are few and far between. On the other hand, certification programs in Java programming are more readily available online. 

Diploma programs typically run for around a year to complete and include a wide range of topics, including but not limited to the following: programming in Java and JavaScript, files, control statements, and other programming languages and operating systems.

Some Common Java Developer Interview Questions

You can expect these kinds of questions during an interview:

Question#1: Can you give me a rundown of the different features of the Java programming language?

(This is an icebreaker. The interviewer will ask this question to initiate the conversion and to get an idea of your knowledge and hands-on experience. Based on the answer to this question, they will come up with the following questions.)

Expected Answer: The features of Java make it one of the most popular programming languages in the world. It is simple to learn (similar to C++) when given consistent efforts, allows managing codes with objects despite not being fully object-oriented, portable across multiple platforms, and is an independent language due to having its platform for executing codes. 

Also, it is secured with exception handling mechanisms, robust due to its automatic garbage collection concept, a one-stop solution for creating distributed apps, and is considered a dynamic programming language as it supports loading of classes based on demands.

Question#2: What are access modifiers? How are they used in Java?

(This time, the interviewer has jumped to the technical part. Generally, a technical question can be recognized by looking at their structures, consisting of two parts. First, you are asked to brief a jargon, and then they expect a possible explanation for how it can be used in a given scenario.)

Expected Answer: In Java, access modifiers define the accessibility of a field, class, method, or constructor. We can adjust the access levels by using the following four types of access modifiers keywords:

  • Public: A public modifier's access level can be found everywhere. It is accessible from both inside and outside of the class and inside and outside of the package.
  • Private: A private modifier's access level is restricted to the class. That means it is not accessible from outside the class.
  • Protected: A protected modifier's access level is inside and outside the package via a child class. If the child class is not created, it’s impossible to access it outside the package.
  • Default: A default modifier’s access level is restricted inside the package only. In case we don’t choose any access level, the default will be applicable.

Question#3: Explain JDBC API. How is it used in Java?

(The interviewer is throwing another technical question. The safest way is to keep your answer precise. If they want to go deeper into the topic, the next question will be a follow-up to this one.)

Expected Answer: Java Database Connectivity, in short JDBC, is an API that allows us to connect and run queries on a database. It is composed of two types of packages such as java.sql and javax.sql. This API uses JDBC drivers to connect the database. Four types of JDBC drivers are available, they are:

  • JDBC-ODBC Bridge Driver: This driver uses the JDBC API to connect to another API. For instance, ODBC.
  • Middleware Driver: It establishes communication with a middleware server with the help of a pure Java client.
  • Native Code Driver: It is responsible for providing an interface between Java and database clients.
  • All Java Driver: These are pure Java drivers. They execute network protocols for only certain types of data sources.

Question#4: There is a contradiction regarding whether Java is a pass-by-value or a pass-by-reference. What’s your opinion on it, and why?

(Although it’s a technical question, the answer must include your opinion. For some opinionated questions, there can be no definitive answers. These questions are asked when the interviewer just tries to figure out where you take a stand for a certain scenario. However, for this particular question, there is a right answer. So, answering correctly will increase your possibility of being hired.)

Expected Answer: This contradiction is not unknown to me as well. However, as explained by Java Spec, the object reference is passed by value in Java and never by reference. This signifies that a value is copied to a new variable and sent over to a method. In Java, it makes no difference whether the value is a primitive or an address of an object. It is always passed by value.

Question#5: How is the final keyword used in Java?

(It’s an operational question. These types of questions are asked when the interviewer tries to understand how you will approach certain tasks necessary for this position. Try to answer to the point and let them hit you up with a follow-up question in case of more information.)

Expected Answer: In Java, the final keyword is used to restrict access to a variable, class, or method.

Variable: When a variable is initialized using the final keyword, its value can't be changed further. It stays constant. We will get a compilation error if we try to modify the value of a final variable. A final variable devoid of value is known as the blank final variable.

  • Method: When a method is declared final, no subclass can override it.
  • Class: Declaring a class as the final means other classes can’t inherit from it. We will get a compilation error if another class tries to extend it.

Some Additional Questions

Question#6: Are you familiar with JIT? What does it do?

Answer: The full form of JIT is a just-in-time compiler. It is responsible for enhancing the performance of Java applications during run time. Whenever a method gets called, this compiler gets activated and converts that method's bytecodes into native machine code. 

This compiler is preferred over conventional compilers as it employs different levels of optimizations consuming less memory.

Question#7: What do you know about Java class loaders?

Answer: In Java, class loaders are in charge of dynamically loading the classes into the JVM (Java Virtual Machine) during compilation. The JRE (Java Runtime Environment) doesn't need to know the details of the files and their systems. All it has to do is call the class loaders, and they will load classes into the memory.

Question#8: Explain copy constructor in Java.

Answer: A copy constructor is capable of using an object from the same Java class to create a new object. There are a lot of times when we struggle to copy an existing object that contains a lot of fields, and this is where this constructor comes into action.

Question#9: What is JDK? What are its variants? 

Answer: JDK stands for Java Development Kit. It is composed of JRE (Java Runtime Environment) and a bunch of development tools that are used to develop Java applications from scratch. The variants of JDK released by Oracle Corporation include:

  • Standard Edition JDK
  • Enterprise Edition JDK
  • Micro Edition Java JDK

Question#10: What do you understand by method overloading in Java?

Answer: With Java's method, an overloading feature, classes can have multiple methods of the same name but distinct parameters. It’s a well-known method for enhancing the program's readability. By overloading, we can call the same methods for different data types. In Java, we can overload methods in two ways:

  • By changing the data types.
  • By changing the number of parameters.

Developer working alone in his room

Career Path of a Java Developer

This is the usual career path for a Java developer, but in reality, you can branch off and do many more things as the usage of Java is dynamic and widespread!

1. Entry Level Java Developer

It's the starting point for a career as a software engineer. The engineer is responsible for all aspects of software development, including drafting, evaluating, testing, and fixing bugs. They usually collaborate while being supervised by more experienced members of the team.

The developer should make it their top priority right now to study all industry norms and protocols. Learning new skills can help one become more proficient in their current role, advance one's career within the same company, or perhaps move on to a better company altogether. One of the best things about Java is the abundance of employment opportunities.

2. Senior Java Developer

On most projects, the buck stops with a senior developer. They also contribute to the company's codebase and communicate their findings to upper management. They must also act as a mentor to programmers who are fresh to the team or the project at hand. This position is representative of what a developer typically does for a living.

3. Java Architect

A Java architect's job is to architect the framework within which a Java program will operate. They provide a framework for classifying the various logical levels, which is useful for allocating tasks to different project team members.

A good architect will design cutting-edge tools that work well together and are optimal for the intended application.

Current and Future Demand for Java Developers

One of the jobs that are essential to the smooth operation of today's world is that of the programmer. Without them, it's hard to fathom how the modern world would run. It is, therefore, not surprising that there is such a large amount of interest.

Programmers are in high demand in today's job market and command higher pay, in addition to having access to extensive prospects for professional growth, working independently, and performing their duties from a remote location.

However, will there always be a need for people to write programs in Java? Without a doubt, the answer is a YES!

It is an excellent choice for the development of streaming apps due to the reactive capabilities that it possesses.

Java is still necessary for the web, artificial intelligence, mobile, big data, and technology such as blockchain. It is possible to develop serverless and FaaS (function as a service) apps that have a high level of functionality. The software platform Java is still widely used by major digital companies such as Airbnb, Netflix, and Uber, amongst others.

Salary Expectations

A Java developer may expect to earn about 110k USD yearly.

Josh Evan

Written by:

Josh Evan

Josh Evan is the professional career counselor and career development writer at When Work Works. He loves to see people from this field succeed through initiating the right thing in the right way. He never tells; he shows the way.We appointed John not because of his impressive CV. It was his counseling charisma which stood out of everything. He can implant idea, confidence and productive thoughts into mind almost effortlessly. His pen and mouth both speak for the greater good.

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