5 Crucial Interview Questions for Junior Java Developers


Welcome to the world of Java development, where the quality of one’s skill set is the standard for ranking. That is to say that anyone can be a Junior, middle-level, or senior developer once they have mastered the skills to upgrade to the next level. It’s like playing the popular Asphalt 9 racing game. You move to a new level of expertise once you have raced certain laps and mastered every racing pitch in the stages crossed. 


In Java development, developers are divided into levels based on their skill set and experience- Junior developers, middle-level developers, and senior developers. A junior developer has the potential to become a middle developer and a senior Java developer as long as he continues to improve, take on new tasks, create solutions, and remain focused on growth. But that is not all.


Welcome to the Mind of a Junior Java Developer 

Junior Java developers are newbies, graduates who have spent time learning and mastering the basics of Javascript. Junior devs have little or no prior working experience and need much of it to build their portfolio. This means that job applications, successful and unsuccessful interviews characterize a Junior developer’s growth process.


Junior developers can be extremely picky with offers. Junior developers have a growth mindset, and away from the remuneration they would get for a job well done, they also want to work in an environment that challenges their creativity, pushes them to be better, and gives them a wealth of experience. A junior developer decides after the first interview whether or not an organization is a good fit for them. Hence, making the right impression begins with your choice of interview questions. 


This article is your biggest ally for nailing the right junior Java developer. The five crucial interview questions discussed in the succeeding paragraphs are curated in ways that test the knowledgeability, creativity, and time management skills of the junior developer you intend to hire. 


However, being abreast with the skillset required of a junior Java developer is important. Knowing the minimum skills every junior Java developer should possess will ensure that you have a minimum requirement for applicants who qualify for proper interview and aptitude test screening.



What Skills to Expect From a Junior Java Developer

A junior Java developer knows Java, especially the basics and the applications of Java in building solutions. Therefore, a Junior Java developer is expected to have the following skill set: 

  • At least one year of experience. 

  • A desire to learn.

  • A concrete understanding of software interaction with hardware.

  • The dependent relationship between software and hardware.

  • Knowledge of Java syntax.

  • Knowledge of collections and multithreading.

  • Knowledge of coding tools like Eclipse, IntelliJ IDEA, or NetBeans.

  • Knowledge of version-control systems and services such as GitHub and GitLab.

  • An understanding of project-building frameworks like Spring and Spring Boot.

  • How to use Object-relational mapping.

  • The ability to use building automation tools like Gradle and Maven.

  • Fluidity with tools for unit testing like JUnit and Mockito.

  • Basic knowledge of other common programming languages, like JavaScript, and technologies like HTML5/CSS3.

  • The ability to correctly program and write codes.

  • Knowledge of databases and operating systems.

  • Basic knowledge of Computer Science is a foundation of knowledge for any profession in software development.

  • The ability to learn new software platforms and technologies quickly.

  • Ability to follow instructions and work in a team environment 


These skill sets are important because when a junior developer is hired, he will be expected to write, maintain, and fix small bugs and minor code mistakes. He will also be responsible for the backend side of tools/features, the codebase, and the project’s structure, working with the codebase without doing anything too complicated, defining features set by the supervising software developer, general concept, and markup.


As Junior developers become better and can be trusted with more tasks, they are often given tasks that could cut across, focusing on the backend in minor aspects, assisting initial stages of project planning, and analyzing the project’s technical requirements. 


In other words, a good Junior software engineer should be ready for anything. At first, the junior designation means working under the supervision of senior developers in the department, but it turns out that it gets more complex than this. Competent Junior Java developers may need to meet with clients to review their preferences and provide advice.


So what are the 5 Crucial Interview Questions for Junior Java Developers that could help you hire the right Junior developer for your team or organization? 


5 Crucial Interview Questions for Junior Java Developers

There are no hard and fast rules to these questions. Junior Java developers must have encountered these things during their introductory phases to Javascript. The questions are not difficult, but will try your knowledge and creativity. 

Question 1. 

How Does Java Achieve Platform Independence?


Platform independence in Java means that the Java program can be installed and run on any platform or operating system without glitches or changes in the general interface. Platform independence is achieved in Java by bytecode.


Bytecode is an intermediate code produced by the compiler when the Java program runs on a particular machine. This intermediate code produced is sent to the part of the computer’s RAM called the Java Virtual Machine (JVM), and the Java Virtual machine converts the bytecodes into native machine code.


Question 2.

Explain the main difference between fail-fast and fail-safe iterators.


The main difference between fail-fast and fail-safe iterators is the ease of modification during iteration. While fail-fast iterators operate directly on the collection itself, Fail-safe iterators operate on a cloned copy. This means that during iteration, fail-fast iterators fail as soon as they realize that the collection has been modified. In contrast, fail-safe iterators do not throw any exception if the collection is modified during iteration.


Question 3

What are loops in Java? – Explain the three types of loops 


Loops are mechanisms Java uses to execute a statement or a block of statements repeatedly. There are three types of loops in Java. They are:


1. For Loops, used in Java to execute statements repeatedly for a given number of times.

2. While Loops are used when determined statements need to be executed repeatedly until a condition is fulfilled.  In While Loops, the condition is checked before the execution of block statements.

3. Do While Loops, the same as While loops with the only difference being that the condition is checked after the execution of block statements. 


Question 4

What is the Difference Between ArrayList and HashSet in Java?



  1. ArrayList implements a list interface, while HashSet implements the set interface.

  2. ArrayList allows duplicate values, while HashSet doesn’t allow duplicate values.

  3. ArrayList has three constructors, which are ArrayList (), ArrayList (int capacity), and ArrayList (int Collection c). In comparison, HashSet has four constructors, which are HashSet (), HashSet (int capacity), HashSet (Collection c), and HashSet (int capacity, float load factor).

  4. ArrayList maintains the order of the objects in which they are inserted, while HashSet doesn’t maintain any order.

  5. ArrayList allows adding any number of null values, while HashSet allows one null value.

  6. ArrayList has this kind of syntax-ArrayList list=new ArrayList (), while HashSet has this kind- HashSet set=new HashSet ();


Question 5

What is a Java ClassLoader? Explain the various access specifiers for Java classes.


The Java Classloader is part of the Java runtime environment that loads classes on demand into the Java Virtual Machine (JVM). Classes are loaded from the local file system, a remote file system, or even from the web.

When the JVM is started, three class loaders are used:

1.   Bootstrap Classloader: Loads core Java API file rt.jar from the folder.

2.   Extension Classloader: Loads jar files from the folder.

3.   System Classloader: Loads jar files from the path specified in the CLASSPATH environment variable.


Access specifiers are the keywords used before a class name that defines the access scope. 

There are four types of access specifiers:

1.  Private: A variable is private if it can be accessed only from the same class to which it belongs.

2.  Public: Methods and variables with public access can be accessed by all the other classes in the project.

3.  Protected: A variable is protected if it can be accessed within the same package classes and subclasses of any other packages.

4.  Default: Methods and variables can be accessed only from the same package and not outside its native package.



There is a list of other questions you can use to test the competence of a junior developer. In fact, these five questions stated in this article are only here to reduce the recrutment time. Feel free to add as many questions as possible to the list. 

Or, let us handle that aspect of recruitment for your organization. Droomwork has an up-to-date database of recruiting questions and requirements for developers at different levels. 




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