49 Core Java interview questions for experienced programmers

Hiring a Core Java developer can be tricky if you aren’t an experienced developer yourself, as you must effectively analyze candidates’ soft and hard skills and consider whether their experience level matches your expectations.

With a Java skill test and related programming skills tests, you can evaluate multiple skills with minimal stress and effort. All that’s required is for you to invite candidates to complete an assessment.

If you’re having problems building your Core Java interview questions list, there’s no need to worry. Here are 49 questions you can ask experienced candidates to evaluate their abilities and knowledge.

19 Core Java interview questions for experienced talent about technical knowledge

For the technical part of the interview, these 19 Core Java interview questions for experienced talent are ideal for testing their knowledge. Ask them some of these questions to assess your candidates’ expertise.

1. Could you explain why inheritance isn’t as beneficial as composition?

2. What do you understand about the term composition?

3. What do you understand about the term aggregation?

4. Could you tell us how composition is different from aggregation?

5. Do you know what a constructor is in Core Java?

6. Could you tell us how many constructors exist in Core Java?

7. What do you understand about default constructors?

8. Can you tell us whether constructors are inherited? Explain your answer.

9. Can programs exceed a memory limit even if they have a garbage collector?

10. What do you know about synchronization? Can you tell us why it’s necessary?

11. Do you know what the varargs feature is? Which symbol would you use for this?

12. Name one advantage of using an ordered array in Core Java.

13. Name one disadvantage of using an ordered array in Core Java.

14. Have you used marker interfaces in your projects? Can you explain what they are?

15. What do you know about double brace initialization in Core Java?

16. Could you tell us how to make an object garbage-collection eligible?

17. Can you name a few examples of Java design pattern categories?

18. How have your soft skills helped you complete Core Java programming duties?

19. Is it true that the length() method in the String class doesn’t provide accurate results?

5 Core Java interview questions for experienced programmers with sample answers

When reviewing your candidates’ technical interview question responses, have these sample answers ready so you can quickly check the depth of their knowledge.

1. How have your soft skills helped you complete Core Java programming responsibilities?

Java developers should have hard and soft skills to complete Core Java programming responsibilities. Although technical skills may seem more important, soft skills such as time management, communication, and motivation are equally crucial, helping applicants to:

• Efficiently prioritize tasks and projects

• Take feedback on board

• Stay productive when completing tasks

For example, developers must be motivated and organized when developing an application to finish the work within a specific time. Since project delays can harm your company’s relationship with its clients, it’s best to review these soft skills before you hire someone.

But what’s the best way to assess your candidates’ soft skills? It’s easy with our Time Management, Communication, and Motivation skill tests. Use them to check who among your candidates has these abilities.

2. Could you tell us why inheritance isn’t as beneficial as composition?

Senior applicants will know why inheritance is less beneficial than composition in Core Java and respond based on their experience. 

Candidates should know that Core Java doesn’t allow multiple inheritances and that composition is ideal for preventing encapsulation breakage.

Candidates might have a couple of other insights when responding to this question. 

They may mention that composition’s loosely coupled nature is more advantageous than inheritance’s tightly coupled state and that developers can complete unit testing with composition – which isn’t possible with inheritance.

3. Can programs exceed a memory limit even with a garbage collector?

The simple answer to this question is that programs can run out of memory despite having a garbage collector. However, applicants can provide more detail. They should explain that although the garbage collector eliminates objects the program doesn’t require, some might remain in the scope.

Since a few objects may still exist, they can consume memory, which requires developers to dereference objects when they have completed their work.

4. What do you know about synchronization? Can you tell us why it’s necessary?

Synchronization is a process that makes concurrent process execution possible in Java. It’s particularly useful when several threads share one resource. 

Listen out for responses that elaborate on the advantage of synchronization and explain that the process facilitates reliable communication from one thread to another.

5. Do you understand what the varargs feature is? Which symbol would you use for this?

To show their knowledge of Core Java’s essential features, candidates should know that varargs mean variable arguments. But to provide more information, they might explain that engineers introduced the feature in Java 5, which enables developers to:

• Assign multiple arguments

• Support parameters of one type

Skilled and experienced candidates should explain that the ellipsis symbol […] represents the varargs feature.

10 Core Java interview questions for experienced talent about technical processes

Processes and methods for coding an application in Core Java are fundamental – assess your applicants’ knowledge of some essential technical techniques and strategies with some of these questions.

1. How would you print messages on the console? Which method would you use?

2. Which method should developers use to complete dependency injection?

3. Which method would you use to set up the spring bean scope?

4. Is it possible to release a lock on a thread with the sleep() method? 

5. How different is creating a string with new() from forming a literal one?

6. Can you tell us if making a constructor final is possible? Explain your answer.

7. How much do you know about the Java thread lifecycle? Name each step.

8. Do you understand what a memory leak means? Can you tell us what causes it?

9. Can developers import the same package two times in Java?

10. Can developers import only the main package if it has several sub-packages?

5 technical Core Java interview questions for experienced talent with sample answers

Here are five sample answers to the Core Java interview questions about technical processes to help you review your candidates’ knowledge.

1. Which method should developers use to complete dependency injection?

Although there’s no obligatory way to complete dependency injection, there is a recommended method. Candidates should know that developers should use setters if they’re completing optional dependency injection and constructor arguments for mandatory injection.

Knowing why these methods are recommended is important – check if candidates can explain this. For example, they might know that constructors make injecting values into immutable fields easy and enable the program to read them more easily.

2. Which method would you use to set up the spring bean scope?

One of the straightforward ways to set up the spring bean scope is to use a specific annotation or attribute. Applicants with advanced knowledge can specify that the @Scope annotation or attribute can facilitate this process, giving developers more control over bean instances creation.

If your applicants are eager to impress, they will explain that developers can use the annotation and attributes in XML configuration files.

3. Do you understand what a memory leak means? Can you tell us what causes it?

Although this question is similar to the Core Java interview question about garbage collection, applicants should be able to add more detail when responding. 

A memory leak happens when the garbage collector cannot remove – and the system cannot reference –  unused objects. If the garbage collector doesn’t free this memory, this creates a memory leak. 

However, a few other memory leak causes exist, such as:

• Unbounded caches

• Too much page swapping

• Failure to delete custom objects before inserting them

Using the garbage collector correctly is crucial, as it can run 17% slower with three times as much memory. Check if your candidates understand the link between memory and garbage collectors to ensure their applications run efficiently.

4. How much do you know about the Java thread lifecycle? Name each stage.

If your candidates have a deep, technical understanding of the Java thread lifecycle, they may be ideal for a second interview process. Their answer should mention that there are five stages in the process, including:

• New: at this stage, developers have not invoked the start() method but have created the thread.

• Runnable: this stage occurs after the developer invokes the start() method but before the Java virtual machine invokes the run() method

• Running: at this stage, the Java virtual machine invokes the run() method, and the thread begins to execute

• Non-Runnable: this stage occurs when the thread cannot run when it is blocked or in a waiting state

• Terminated: at this stage, the Java virtual machine has completed the run() method execution

5. Can developers import the same package two times in Java?

Although developers can import the same package twice, the action is usually redundant. Candidates should know that the Java virtual machine typically loads packages and classes once, no matter how many times they import them. So even though this process won’t cause any problems, it can waste time. 

10 Core Java interview questions for experienced talent about operators

If you want to discover more about your applicants’ operator knowledge, ask them a few of these 10 Core Java interview questions for experienced talent.

1. Do you understand how the >>> operator is different from the >> operator?

2. Could you explain the new() operator’s function in Java?

3. Could you explain the newInstance() operator’s function in Java?

4. Do you know how Java’s new() and newInstance() operators differ?

5. Can you explain how the equals() method differs from the equality operator?

6. Can you explain what a unary operator is in Java?

7. What does the ! operator mean in Core Java?

8. What does the != operator mean in Core Java?

9. What does the ?: operator mean in Core Java?

10. Can you explain what a conditional operator is in Java?

5 operator-related Core Java interview questions for experienced talent and sample answers

To review your candidates’ operator-related responses, check the sample answers to these five fundamental Core Java interview questions for experienced talent.

1. Do you understand how the >>> operator is different from the >> operator?

The key to assessing responses to this Core Java interview question is to consider if applicants can provide one main difference between the two operators. 

Candidates should know that >> is a bitwise right shift operator that moves each bit to the right and retains the signed bit. They should then explain that >>> is a bitwise right shift operator that provides a trailing zero.

Adding more details to their response will help candidates prove their expertise. If applicants know that the >>> operator does not retain the signed bit, they likely have a good knowledge of operators in Core Java.

2. Could you explain what the new() operator’s function is in Java?

Developers use the new() operator to create objects in Java. It works through class instantiation, helping programmers to allocate memory for new objects. The operator also returns a specific reference to the allocated memory.

If you want to assess your candidates’ knowledge more deeply, ask them questions to see if they know how the new() operator relates to the object constructor. They should know that this operator functions by invoking the constructor. 

3. Could you explain the newInstance() operator’s function in Java?

What’s important when assessing your applicants’ responses to this question is to check if they know when developers should use the newInstance() operator. Expert programmers will know this operator is ideal when developers don’t know the class name required to create an object. 

They’ll also understand that it functions well when developers need to retrieve the class name from a database, file, or command line argument.

4. Do you know how Java’s new() and newInstance() operators are different?

Even though the new() and newInstance() operators create objects, one key difference exists between them. Developers should use the new() operator if they already know the name of the class when creating the object and the newInstance() operator when they don’t.

Give top marks to candidates who understand that newInstance() is a dynamic method that can help developers load classes from remote sources.

5. Can you explain how the equals() method differs from the equality operator?

Applicants should know that the equals() method enables developers to compare two objects based on the content of those objects. They should then explain that the equality operator in Java helps developers compare primitive types of data and objects based on their memory location.

If they want to provide more detail, candidates will mention that the equality operator also checks if the two objects point to the same memory locations. 

10 skill-related Core Java interview questions for experienced programmers

Core Java skills are critical for Core Java developers. Ensure you review their abilities by asking them some of these 10 Core Java interview questions for experienced programmers.

1. Do you have a good knowledge of object-oriented programming?

2. Why are Java skills important for Core Java developers?

3. Tell us about your application programming interface knowledge.

4. How are Spring Boot skills linked to Core Java? Why are they important?

5. Do you understand what the Java virtual machine is?

6. Explain how good communication helps developers collaborate on projects.

7. Why is problem-solving a fundamental skill for Java developers?

8. Why are critical-thinking skills crucial for Core Java developers?

9. Do you understand why attention to detail is crucial for Core Java developers?

10. Are you familiar with DevOps? Why are DevOps skills necessary for Core Java developers?

5 skill-related Core Java interview questions for experienced talent with sample answers

Check out the answers to these five skill-related Core Java interview questions to review your candidates’ responses and quickly assess their abilities.

1. Are you familiar with DevOps? Why are DevOps skills necessary for Core Java developers?

Applicants should know that the DevOps model enables teams to implement development, testing, deployment, and application operation. With sufficient DevOps skills, applicants can easily complete continuous integration, Java development automation, and quick feedback implementation. 

Looking for a quick method to assess your interviewees’ DevOps skills before the interview? Use our DevOps skill test to review four essential DevOps subskills.

2. How are Spring Boot skills linked to Core Java? Why are they important?

The great thing about Spring Boot skills is that they facilitate the web application and microservices development process for Java developers. Programmers with this skill can use this open-source framework without integrating special tools. With the right skills, they can use any text editor or integrated development environment to complete their projects.

Therefore, it’s a good idea to assess your candidates’ Spring Boot knowledge with a data-driven skill test, such as our Spring test. This process will help you learn if their abilities are ideal for your company. 

3. Why is problem-solving a fundamental skill for Java developers?

The entire development lifecycle relies on problem-solving skills, which developers should hone for their projects. It’s a critical skill because developers must notice problems and develop strategies to solve issues before delivering software or applications.

After code reviews and software testing, developers must also make changes to the code in line with the feedback, which problem-solving can help with. 63% of developers spend 30 minutes working on projects that require problem-solving, but it’s still vital to assess their abilities and determine if they match your role.

With this in mind, it’s worth asking candidates to complete a Problem Solving skill test before you hire someone to evaluate this essential skill. Our test will reveal the programmers with the most advanced problem-solving skills and experience.

4. Why are critical-thinking skills crucial for Core Java developers?

With critical-thinking skills, Core Java developers can think of unique and viable strategies to handle errors. Without it, they will struggle to select the best methods to resolve problems in their code or application.

For instance, if testing reveals a bug that affects the user experience, candidates can solve this using critical-thinking skills and make the user experience smoother.

Many applicants might complete hackathons or work on projects to develop their critical-thinking skills, but if you need a more quantitative way to assess this, use our Critical Thinking skill test.  

5. Do you understand why attention to detail is crucial for Core Java developers?

Attention to detail is vital for most tasks Core Java developers complete. It can help programmers notice the tiniest errors in their code, which would otherwise ruin the entire program. 

This skill also has other positive consequences for software development. It ensures systems can read and understand the code thanks to the correct syntax and makes code modification easier.

One way to assess applicants’ attention to detail is to use our Attention to Detail test. Integrate it into your candidates’ Core Java assessment for easy candidate evaluation.

When should you use Core Java interview questions for experienced talent?

You’ve now got a list of interview questions, but it’s important to consider when to use them during the hiring process – which should happen after candidates complete assessments. 

You can remove unskilled candidates immediately based on their lack of skills when you ask applicants to complete the five tests in your assessment.

With this strategy, no unsuitable candidates will enter the interview stage, saving you time, effort, and extra administration work. And combined, these methods give you statistical and qualitative information to help you assess candidates thoroughly.

Hire skilled programmers using Core Java interview questions for experienced talent

There isn’t an easier way to assess applicants than to use Core Java interview questions for experienced talent and skill testing, which is why we recommend this easy strategy.

The optimum thing about these methods is the time you’ll save by avoiding resume screening methods because skill testing is the perfect replacement for resume screening.

But what are your next actions? We suggest you sign up to TestGorilla for free or register for a demonstration to learn more about custom questions, branding, and the best way to send candidates invitations.

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