14 Java advanced interview questions and answers (with tips)

Updated 8 February 2023

Java is one of the most widely used programming languages in the world. A hiring manager may assess your knowledge of this language during an interview for a position in software engineering or software development. Learning how to answer advanced Java interview questions can help improve your chances of success. In this article, we discuss common Java advanced interview questions and explore Java interview tips.

Java advanced interview questions

Here are a few Java advanced interview questions and example answers to help you prepare:

What does JIT mean in Java?

A hiring manager may ask this question to evaluate your knowledge of architecture. When answering this question, you can explain the purpose of JIT and when it becomes active. You can also highlight a few of its advantages.

Example answer: 'JIT is an abbreviation for just in time. It's a computer-intensive program that optimises the performance of the Java application. JIT is a compiler that becomes active every time you use a Java method. The JIT compiler converts code into native machine code. Most people prefer this compiler because it uses different optimisation levels and requires less memory usage.'

What's a race condition in Java?

Employers may ask this question to gauge your Java proficiency. When answering this question, mention when it occurs and why.

Example answer: 'A race condition occurs when two programs run in parallel while multiple threads simultaneously raise requests for resource allocation.'

Name two differences between a class and an object

Recruiters may ask this question to evaluate your skill level. You can answer this question by mentioning the differences in the behaviour and virtual reality of these concepts.

Example answer: 'One difference is that a class is a construct that lacks reality in a virtual space, while an object has reality in a space. Another is that a class shows no behaviour on its own but represents a blueprint of an object. Comparatively, an object displays a specific behaviour.'

What's the main difference between local and instance variables?

A hiring manager typically looks for a specific difference between these two concepts when asking this question. They're evaluating your understanding of the two terms.

Example answer: 'You can only use a local variable in a specific block, method or constructor while conforming to specific methods is unnecessary for instance variables.'

What are garbage collectors in Java?

A hiring manager typically asks this question to gauge your knowledge of garbage collectors. You can provide the definition in your response.

Example answer: 'When objects are no longer in use, you typically use garbage collectors to free the occupied memory. An object becomes unusable in the absence of a thread to access it.'

What's an instance variable?

Hiring managers may ask this question to assess your Java proficiency. You can answer this question by defining the term and describing how it reacts to changes.

Example answer: 'An instance variable refers to a variable bound to an object, specified inside a class and a method on the outside. When objects use instance variables, each creates its variable version. A change to an instance variable confines it to a specific instance and doesn't appear in the other instances of that specific variable.'

Name the access modifiers in Java

Here, you can list all the access modifiers in Java that you know. The interviewer may ask this question to gauge your memory and knowledge.

Example answer: 'Java mainly includes public, private, default and protected access modifiers.'

What's data abstraction in Java?

Data abstraction is an important feature in the Java framework. Your response can demonstrate your knowledge of this feature and that you understand its utilisation.

Example answer: 'Data abstraction is a feature that limits the visibility of objects and allows users to access and view only the necessary data or information. This feature hides the implementation details from users since this information is unnecessary.'

What do constructors do in Java, and what's the difference between parameterised and default constructors?

Your response to this question requires you to demonstrate your knowledge of constructors. You can provide information on how and when to use them.

Example answer: 'Constructors consist of blocks of code and help to initialise objects in Java. Parameterised constructors use the values you provide to initialise an object's instance variables, while default constructors use default values to initialise the instance variables. Failing to define a constructor during object creation generates a default constructor.'

What disqualifies Java from being completely object-oriented?

With this question, the interviewer typically assesses your understanding of the unique features of the Java language. You can demonstrate your proficiency by mentioning some data types that aren't objects.

Example answer: 'Java contains data types that aren't purely object-oriented, which is why it's not a completely object-oriented programming language. Some of the non-object data types include byte, char, int, float, short, long, double and Boolean.'

What's the difference between stack memory and heap memory in Java?

A software engineer or developer requires a grasp of the main Java functionalities, including memory. You can provide a response that defines these two memory types to help you distinguish the differences.

Example answer: 'Stack memory is smaller than heap memory. Stack memory is only relevant from the start to the end of a thread's execution. In comparison, heap memory is relevant from the start of the execution until the end of the application. The heap memory typically represents the main storage location for most objects in Java.'

Which frameworks are popular for building Java applications and programs?

The interviewer typically evaluates your attention to detail and research skills with this question. Knowing the popular frameworks can also demonstrate your ability to stay updated with industry trends.

Example answer: 'Some of the common frameworks that developers use to build Java programs and applications include Spring, ReactJS, React Native and Angular.'

What are break and continue statements?

An interviewer typically asks this question to assess your knowledge of these two statements. You can respond by providing their definitions, similarities and differences.

Example answer: 'Both continue and break statements represent control statements that you use to transfer control to a different part of your program. You can use both within a loop. Encountering a continue statement within a loop bypasses the loop's iteration, transferring control to its top. Encountering a break statement terminates the loop, transferring control to the first statement outside the loop.'

Why can you run Java on any platform?

As a software developer or engineer, it's important to know the advantages of different programming languages. Recruiters ask this question to evaluate your knowledge of the various programming languages. You can demonstrate your understanding by explaining the benefits of Java and why most people prefer it.

Example answer: 'Java is an independent language, which means you can use it on any platform, such as Linux or Windows. It differs from other programming languages, such as C++, which requires porting every time. Java can achieve this via the bytecode and Java virtual machine.'

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Java interview tips

Java advanced interview questions can be technical and daunting. As a potential candidate, it's important that you effectively convey your knowledge of this language to the interviewer. Here are a few tips that can help you prepare for a Java Interview to improve your chances of success:

Review your Java knowledge: Regardless of whether you use Java skills in your current job, consider reviewing your basic knowledge of this language. You can evaluate your understanding of Java by reviewing your resume and previous roles to help you identify areas that require improvement.
Conduct additional research on Java: Consider conducting additional research on areas involving Java that are unclear. For example, if you're unfamiliar with Java functionalities, research this area to help you confidently answer questions.
Research common Java interview questions: Consider researching common Java interview questions to give you an idea of what to expect. Doing this may also help refresh your memory regarding Java facts.
Practice answering the interview questions: Practice answering questions about Java by requesting a friend or family member to play the role of a hiring manager. This can help you organise your answers, while feedback from your family and friends may provide you with a fresh perspective.

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