Mastering Test Tasks: A Guide for Junior Java Developers

Landing a junior Java developer job is a goal of every learner, and solving test tasks is a crucial factor in achieving it. After all, you must impress your potential employer while feeling nervous and not confident enough. But don’t worry: we’ve collected tips and task examples to help you prepare for anything!

What Do Test Tasks Look Like?

Even though nobody expects junior developers to have vast experience or a huge portfolio of projects, employers still need to access your coding skills. Solving tasks is the best way to do it. So, you’re often presented with several simple problems regarding Java core concepts and data structures. Here are typical examples:

• Ask a user to enter two numbers and calculate the sum.
• Implement a Java method to check if an entered number is prime.
• Create a calculator with basic functions (add, subtract, multiply, divide).
• Find the duplicate characters in a string.
• Swap two numbers without introducing a third variable.
• Write a Java method to reverse an entered string.
• Check if two strings are anagrams of each other.
• Generate and validate random passwords based on specific criteria (e.g., length, character types).

To test your understanding of the OOP concepts, a potential employer may ask you to:

• Create a class hierarchy for geometric shapes (rectangle, triangle, etc.) and write methods to calculate area and perimeter.
• Design a class hierarchy for a library management system. Include parent and child classes, demonstrating inheritance and proper encapsulation of attributes and methods.
• Design a simple banking system with methods for deposit, withdrawal, and balance inquiry.

Most likely, you’ll need to demonstrate your comprehension of algorithms by solving tasks such as:

• Write code to perform a linear search on an array of integers.
• Write a method to alphabetically sort an array of strings using the bubble sort algorithm.

Other topics that you may encounter during job interviews include:

• Exception Handling. For example, you may be asked to implement a Java method to divide two numbers, catching and handling any possible arithmetic exceptions.
• File I/O. For instance, write code to receive data from a text file, process it, and save the results to another file.
• Multithreading. For example, write a class with synchronized methods to manipulate shared data in a multithreaded environment safely.
• Collections Framework. You may be asked to write a program to demonstrate the use of ArrayList, LinkedList, and HashMap or a program to count the frequency of words in a provided text using a HashMap.
• Unit Testing. For instance, create test cases for the methods you’ve written before.

Sure, the contents of an interview depend on the specific job requirements and company preferences, but if you practice the abovementioned tasks, you have every chance to complete this part of the hiring process successfully. Some tasks may be tricky, but you can prepare to solve them, too. Also, for junior developers, there are optional topics that you may use to impress a potential employer. For example, working with databases (writing a program to connect to a database, retrieving data from a table, and displaying the results) or graphical user interface (GUI) Development (say, designing an app to simulate an address book).

What Makes an Impressive Solution?

Some of the tasks you’ll be given may be “short” (you’ll have only a few hours to solve them), but others may be “long” (you’ll have several days to implement them). In the first case, you must provide a correct solution and write a clean code. In the second case, you may show off a bit and earn some extra points. What are must-haves for your solution besides writing clean code that is easy to read, understand, and maintain?

• A Readme file that provides information about a project, placed in the root directory.
• Using build automation tools like Maven/Gradle.
• Applying SOLID design principles to create more maintainable and flexible solutions.
• Implementing integration and unit tests. Integration tests ensure different components work together correctly, and unit tests focus on testing separate units of code to ensure they behave as expected.

To impress an employer, you can also remember about logging (storing information about the execution of a program, such as errors, warnings, and debug messages), applying CI/CD (Continuous Integration and Continuous Delivery/Continuous Deployment) approaches, uploading your solution on GitHub, etc. It will help you stand out from other candidates.

What Are the Main Steps?

So, you've got the task – what's next? First, don't rush! You should make sure you understand the task correctly. What are the input and output formats? What are the requirements and constraints? Ask clarifying questions and identify edge cases. What's the business scenario of this task, and what's beyond it? This step will demonstrate your problem-solving approach and communication skills. Second, before diving into coding, spend some time planning your solution. Decompose the problem (break it down into small parts). You may also use tools for visualizing, like a diagram. It will help you choose the algorithm to solve the task and explain your logic to interviewers. Third, write a draft code. It may not be perfect, but it should solve the problem and provide the expected outcome. After that, it's time for interactive refactoring to make your code as good as possible. Look for ways to eliminate redundancy wherever you can. Remember clean code principles; a potential employer will definitely pay attention to it. So, choose reasonable variable names, proper indentation, write comments, etc. The next step is about testing and debugging. As mentioned before, unit testing and integration testing are must-haves. Also, test your program on different cases, not just normal but extreme ones. For example, how does your code react to invalid input or empty input? If you find any bugs, fix them. The final step is preparing your solution to give it out. Make sure you haven't skipped any steps. Write a Readme file explaining the logic behind your solution and describing the main classes. Done!

How to Make the Most of a Test Task?

Last but not least, keep in mind that test tasks aren’t just steps on the way to your future jobs. They also help you practice and collect valuable experience. Especially if you remember several important tips:

• You may get nervous; it’s normal for a beginner. In this case, start from what you know the best. After decomposing a task, choose a part you feel the most confident about and implement it first. Then, proceed to the next part; you’ll notice a boost of confidence with every solved piece.
• After you’ve sent your solution, ask for feedback. Even if you don’t get this job, information about your mistakes will help you to land another one. Also, it will show you care.
• Ask your mentor or peers for feedback, too. Accepting criticism isn’t easy, but humility is a virtue for aspiring developers. After all, your goal is to find a job, which means always improving.

Test tasks may be simple or tricky, boring or exciting, short or long. But they are your friends, not foes. Treat them accordingly!