Top 19 Java 8 Interview Questions (2023)

Table of Contents

Java 8: What Is It?

Let’s conduct a quick refresher and define what Java 8 is before we go into the questions. To increase the efficiency with which Java applications may be developed and operated, Java has published Java 8, which was made available to the public on March 14, 2014.

Java is undeniably one of the first names that come to our mind when we talk about software development. A primary driving power behind the global digital lifestyle, Java is an object-oriented programming (OOP) language developed by James A. Gosling in the mid-1990s, together with Patrick Naughton and Mike Sheridan. 

With its many perks that include platform independence, object-oriented nature, and ease of learning, Java finds a host of applications in the software industry; be it Android applications, web-based applications, or desktop GUI applications, computers without Java are legit unimaginable. 

The latest addition to the incredible functionalities of Java is Java 8, an open-source project released on March 18, 2014. Regarded as a revolutionary release for software development platforms, Java 8 is packed with upgrades and new features to the Java programming, tools, libraries, and JVM. The Oracle Corporation currently manages it.

Needless to say, Java 8 interview questions are a hot topic in the field of software development. Moreover, if you are a fresher looking to make it big as a software developer or a related job title, let us walk you through the top Java 8 interview questions and answers you should go through as part of your D-day prep. In addition, we will talk about some popular upGrad courses that will help you get a step closer to your dream job!

Why do you think Java SE 8 is so beneficial?

It has been decided that programmers would benefit greatly from Java SE 8’s release. In particular, these are:

  • It simplifies and clarifies the code. The addition of Lambda Expressions and Functional Interfaces to Java SE 8 increased code reusability.
  • With Java 8, it’s easier to keep up with updates and run tests on code.
  • It aids in the creation of incredibly scalable code and interfaces.
  • Aids in the creation of alternative programs.
  • This facilitated the creation of database-like activities.
  • It boosts the efficiency of a wide range of programs.
  • Java SE 8 allows for more efficient programming.

Top 15 Java 8 Interview Questions and Answers

1. What are the new features added to Java 8?

The essential features included in Java 8 include:

  • Functional interfaces
  • Lambda expression
  • Method references
  • Stream API
  • Date time API
  • Optional
  • Default method
  • Nashorn, JavaScript Engine

2. What are functional interfaces?

Functional interfaces are interfaces that have only one abstract method. These interfaces are implemented using a Lambda expression. Thus, to use a Lambda expression, we need to create a new functional interface or use the predefined one of Java 8.

3. What are the characteristics of the Lambda function?

Main characteristics of the Lambda function include:

  • A method defined as Lambda expression can be passed as a parameter to a different method.
  • There is no requirement of declaring the parameter type since the compiler can fetch the same from the parameter’s value.
  • A method can exist independently without belonging to a class.
  • Using a single parameter does not require parentheses, but the same can be done using multiple parameters.
  • There is no need to use curly braces if the body of expression has only a single statement.

4. What is the structure of the Lambda expression?

Lambda expression has the following structure:

(Argument List) ->{statements;} or

(Argument List) ->{expression;}

5. What are method references?

Method references in Java 8 are a particular type of Lambda expression used for creating simple Lambda expressions by referencing existing methods. The different kinds of method references are – reference to a static method, reference to a constructor, and reference to an instance method.

6. What are Default Methods in Java 8?

Default methods are those methods of the interface which have a body and utilize default keywords. Default methods have the property of backward compatibility. It means that if we add the default method in an interface, we will be able to provide the default implementation without affecting the implementing classes. However, if JDK modifies any interface that does not have the default method, then the classes that implement the said interface will break.

7. What is an optional class?

Optional classes are special wrapper classes in Java 8 for avoiding NullPointerExceptions. NullPointerExceptions occur when we fail to perform Null checks. Optional classes encapsulate optional value that is either present or not.

8. Give some examples of standard Java pre-defined functional interfaces?

The functional interfaces introduced by Java 8 include Predicate, Consumer, Supplier, etc. But popular pre-defined functional interfaces from earlier Java versions include the following:

  • Runnable: For executing the instances of a class over another thread with no return value and no arguments.
  • Comparable: For sorting objects in the natural sort order.
  • Comparator: For sorting different objects as per user-defined order.
  • Callable: For executing the instances of a class over another thread with no arguments. It either throws an exception or returns a value.

9. Name the various categories of pre-defined functional interfaces and their uses.

The various categories of pre-defined functional interfaces are:

  • Function: For transforming arguments in returnable value.
  • Operator: For performing reduction type operations that accept the same input types.
  • Consumer: Accepts arguments but does not return any values.
  • Supplier: Returns a value but does not accept any arguments.
  • Predicate: For performing a test and returning a boolean value.

10. What are some date and time APIs in Java 8?

LocalTime, LocalDate, and LocalDateTime are the core date and time API classes in Java 8. These classes are local to the context of the observer and denote the current time and date in the context of the observer.

11. What were the drawbacks of the old date and time?

The old date and time suffered from the following limitations:

  • Java 8 time and date API meet the ISO standards, but the old date and time had a poor design.
  • While the latest Java 8 date and time API is thread-safe, Java.util.Date was mutable and not thread-safe.
  • In terms of performance, Java 8 is faster than the older date and time regime.

12. What is the difference between a Predicate and a Function?

A Predicate and a Function differ in the following respects:

  • While Predicate has the return type as boolean, Function has the return type as the object.
  • A Predicate is written as Predicate<T> and accepts a single argument. A Function also accepts a single argument but is written as Function<T,R>

Here, T denotes the type of input to the function, and R represents the type of result.

13. What are Stream APIs, and why do we need them?

Stream APIs are a new feature in Java 8, a special class used for processing objects from a source such as Collection.

Stream APIs are needed for:

  • Supporting aggregate operations and simplifying processing
  • Faster processing and better performance
  • Supporting functional-style programming
  • Parallel operations

14. What is the use of the limit() method in Java 8?

The Stream.limit() method is used for specifying the limit of the elements. If we specify the size of the limit(X), it will return the Stream of size ‘X.’

15. What are PermGen and MetaSpace?

Up to Java 7, PermGen was an area used by JVM to store classes. PermGen was replaced by MetaSpace in Java 8.

The major benefit of MetaSpace over PermGen is in terms of size. While PermGen had a fixed maximum size and could not grow dynamically, MetaSpace does not have any size constraint and is capable of dynamic growth.

16. What is Optional in Java 8?

The Optional object is a container for other, non-null objects. Null without a value is represented as a non-mandatory object. 

The Optional class provides many helper methods that may be used in place of testing for null values, allowing for more flexible handling of items that may or may not be accessible. 

Instead of utilizing null references, the Optional class provides a type-level alternative for encoding optional data.

17. What is a Static Method? Why do we need Static methods in Java 8 Interfaces?

Static methods are connected with a certain class or interface and might be either utility or helper methods. It’s not connected to anything in particular.

The following justify our requirement for Static Methods:

  • Instead of placing interface-specific utility methods in a separate Utility class, we may maintain them in the interface itself.
  • There is no need to retain Utility Methods in specialized Utility Classes like Collections, Arrays, etc.
  • Separation of Duties that is easy to understand. That is, there is no need for a separate Utility class to house the many Utility operations available in the Collections API.
  • The API may be easily extended.
  • The API is simple to keep up with.

18. Do you have any background working with Java in a real-world setting?

If you are a seasoned programmer going in for an interview, you should expect this question. To the best of your ability, please respond with an honest account of your prior work in a production setting supporting Java development.

19. Is there a particular Java Developer certification you hold that sets you apart from the competition?

As well as giving you an in-depth understanding of the technology you wish to master, a certification from a reputable organization will look great on your CV.

You may show the interviewer that you have put in the time and effort necessary to understand the technology by working on real-world projects at the industry level, which are included in the certification process.

Certification in a particular technology will lend legitimacy to your resume. It will give you a leg up in terms of information, education, and preparedness for interviews.

Here’s What You Can Do Next

Preparing for tech interviews can be a real hassle if you are not prepared well. By preparation, we do not simply mean going through truckloads of mock questions but also ensuring that your fundamentals are clear as crystal. And what better way to taking the first step towards your goals than signing up with upGrad?

upGrad is a leading online higher education platform offering industry-relevant programs and courses in collaboration with the best-in-class faculty and experts. With top university partners including Liverpool John Moores University, IIIT Bangalore, IIT Madras, and Duke Corporate Education, upGrad amalgamates the best teaching practices and latest technology to provide an immersive and world-class learning experience. upGrad’s educational programs and courses have impacted over 500,000 working professionals. In addition, it has a paid learner base of over 40,000 spread across more than 85 countries.

If you wish to pursue a career in software development or related fields, upGrad’s Master of Science in Computer Science and Executive PG Program in Software Development are two courses you should check out. With upGrad 360-degree career support, peer learning opportunities, and industry networking, the unique programs are curated to help learners master the know-how of software development. 

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  • Master’s degree from the prestigious Liverpool John Moores University.
  • Six unique specializations to choose from – Big Data, Full Stack Development, Blockchain Development, DevOps, Cloud Computing, and Cyber Security.
  • Comprehensive coverage of 30+ programming languages, tools, and software with four years of unlimited content access.
  • More than 500 hours of content with 30+ case studies and projects, 10+ live sessions, and industry mentorship

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  • Recognition from the prestigious IIIT Bangalore.
  • Six unique specializations to choose from – Big Data, Full Stack Development, Blockchain Development, DevOps, Cloud Computing, and Cyber Security.
  • Hands-on exposure to over 30 industry-relevant assignments, case studies, and projects with coverage of 30+ tools and software.
  • 400+ hours of content, over ten live sessions, and mentorship from leading faculty and industry experts.

Gearing Up for the Challenge: Java 8 Coding Interview Questions for Freshers & Experienced and Practical Tests

Java 8 interviews often delve beyond theoretical knowledge, assessing your practical skills and problem-solving prowess through diverse Java 8 coding practice problems and tests. Here’s a roadmap to navigate these assessments:

Showcasing Your Command of Java 8:

Lambda Expressions, Streams, and Functional Interfaces: Be prepared to demonstrate your understanding by tackling Java 8 programming questions specifically designed to leverage these powerful features.

Algorithmic Expertise: Interviewers may present algorithmic challenges, from sorting and searching to collection manipulation, requiring solutions crafted with Java 8 features. So, prepare yourself for java 8 features interview questions.

Design and Architecture for Real-World Scenarios: Design or architecture challenges based on realistic situations might test your ability to propose solutions leveraging Java 8 concepts (classes, interfaces, component interactions).

Refactoring Magic: Breathe new life into code snippets written in older Java versions by refactoring them with efficiency and readability enhancements using Java 8 features.

Debugging and Error Sleuthing: Put your detective skills to the test by identifying and fixing bugs or errors in provided code, applying your Java 8 knowledge and syntax.

Sharpen Your Skills with Practice: Regularly engaging with Java 8 interview coding questions and practical tests is key to honing your Java 8 skills and boosting your interview confidence.

Portfolio and Projects: Beyond the Resume

Java 8 interviews often delve into your real-world experience through portfolio and project discussions. Be ready to address these topics:

Project Scope and Impact: Articulate the scope and objectives of your past projects, highlighting the problems you tackled and the requirements you met.

Tech Stack Savvy: Explain the technologies and frameworks you employed, emphasizing any Java 8 features you strategically leveraged.

Conquering Challenges: Share any obstacles you encountered during your projects and the solutions you devised, showcasing your problem-solving approach and resilience.

Success Stories: Highlight achievements like meeting deadlines, exceeding performance targets, or receiving positive feedback, demonstrating your value contribution.

Lessons Learned: Reflect on the knowledge you gained from your projects, including insights from mistakes and how you’d approach similar projects differently.

By delving into your portfolio and projects, you can weave a compelling narrative that showcases your experience, skills, and achievements to potential employers.

Common Stumbles to Avoid: Pitfalls in Java 8 Interview Questions

Even seasoned developers can make missteps in Java 8 interviews. Here are some common pitfalls to steer clear of:

Unpreparedness: Incomplete understanding of core concepts and inadequate practice can hinder your ability to answer Java 8 interview questions and demonstrate skills.

Shaky Java 8 Foundation: Ensure you have a solid grasp of lambda expressions, streams, and functional interfaces to avoid errors during coding challenges or tests.

Ignoring Edge Cases: Overlooking boundary conditions and edge cases in coding problems or algorithm design can lead to inaccurate results or unexpected behavior.

Communication Barriers: Convey your thought process and reasoning clearly and concisely to avoid misunderstandings. Poor communication can misrepresent your abilities.

Lack of Confidence: Believe in yourself! Project confidence and self-assurance to make a positive impact on the interviewer.

By being aware of these common pitfalls and actively preparing, you can confidently navigate Java 8 interview questions and increase your chances of landing your dream job.

Feedback and Continuous Learning: The Journey Doesn’t End

The interview process doesn’t conclude with the final handshake. Feedbacks are important even for java 8 interview questions for 5 years, 10 years experienced. Here’s how to make the most of the feedback and continue your learning journey:

Self-Reflection: A Valuable Tool: Take time to reflect on your interview experience, identifying areas of strength, weakness, and opportunities for improvement. This introspection will guide your future preparation.

Seeking Feedback: Don’t hesitate to reach out to interviewers for constructive feedback. Their insights can be invaluable for honing your Java 8 programming questions skills.

Embrace Continuous Learning: The world of Java 8 is constantly evolving. Make continuous learning and skill development a top priority. Explore new features, practice coding challenges, and embark on personal projects.

Stay Ahead of the Curve: Actively engage with the Java 8 community by reading blogs, attending conferences, and participating in online forums. Staying up-to-date will keep you competitive in the job market.

Additional Tips for Success

Practice Interviewing: Participating in mock interviews with friends, colleagues, or online platforms can help you become comfortable answering questions under pressure and articulate your thought process effectively.

Showcase Your Passion: Express your genuine enthusiasm for Java 8 and its capabilities. Your passion can be contagious and leave a positive impression on the interviewer.

Ask Relevant Questions: Prepare thoughtful questions to ask the interviewer about the company, team, and role. This demonstrates your interest and initiative.

Follow Up: Thank the interviewer for their time and reiterate your interest in the position. You can also use this opportunity to clarify any points or highlight skills you may not have had a chance to mention in the interview

By mastering Java 8 coding questions, showcasing your projects effectively, and avoiding common pitfalls, you can confidently approach any Java 8 interview. Remember, continuous learning, preparation, and a positive attitude are key to making a strong impression and landing your dream job.


Having a relevant academic degree is the first step towards a bright career in software development. upGrad’s robust courses in Computer Science and Software Development are designed to prepare candidates for varied job roles, including that of Software Developer, Big Data Developer, Data Engineer, Big Data Engineer, and Big Data Architect. The next step is preparing for the job interviews, where questions on the various programming languages and tools are pretty typical. Java being the programming language of choice for developers across multiple platforms, Java 8 interview questions are mandatory in the interviewee’s preparation agenda. 

Why is Java 8 so important?

In most cases, Java 8 significantly improves application performance without any specific tuning. Furthermore, Java 8 features such as the Streams API, Lambda Expressions, and new methods on existing classes contribute towards improving productivity. In addition, Java 8’s Optional feature reduces the chances of NullPointerExceptions and offers significant flexibility while dealing with null values.

What Java programs are asked in interviews?

There are several types of Java programs that are asked in interviews. Such programs can be asked from arrays, loops, control statements, strings, etc. Java basic programs such as prime numbers, Fibonacci series, palindrome numbers, and factorial numbers are also frequently asked.

How do I install Java 1.8 on Windows?

Following are the steps to install Java 1.8 on Windows:
1. Visit the Java .com Manual Download page
2. Click on Windows Online
3. Click Run on the File Download dialogue box to run the file. Else, click Save to save the file for later installation
4. In the next dialogue box that appears, click Install to accept the license terms and start the installation.
5. The installer may present you with options to install various programs when you install Java. Click Next to continue the installation.
6. A few brief dialogues will confirm the last leg of the installation. Click Close on the last dialog to complete the installation process.

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