Technical Interview Questions: Java Knowledge, Skills, and Experience
Java, the Sun Microsystems programming-language and computer platform released in 1995, is everywhere.
It’s in applications and on websites. It’s applied to new laptops, game consoles, and cell phones. It’s fast, reliable, and secure, and thus is used by major tech companies in their systems and applications. Unsurprisingly, updating and debugging Java code has become crucial.
Software development teams frequently rely on Java for front-end development. Hiring managers and engineering leaders find that a large proportion of their computer science engineering candidates know Java, and the technical skills required of those candidates are writing clean code, problem-solving, debugging, and development.
The technical interview for a position requiring Java knowledge traditionally has taken the form of a phone or in-person interview where the candidates answer questions about Java technical vocabulary, Java applications, and projects that require command of Java.
Here are just a few examples from the 50 commonly asked Java programming interview questions:
- What is Java?
- What are the features of Java?
- How does Java enable high performance?
- Name the Java IDE’s.
- What do you mean by Constructor?
- What is meant by the Local variable and the Instance variable?
- What is a class?
- What is an object?
- What are the OOPs concepts?
- What is inheritance?
These are Java questions for freshers, of course. The following are a bit more advanced:
- What’s the difference between HashMap and HashTable?
- What’s the difference between HashSet and TreeSet?
- What’s the difference between Abstract class and Interface?
- What are all the Classes and Interfaces available in the Java Collections?
- Explain about Set and their types in a Collection.
Further down the list are Java interview questions for experienced professionals.
While some of these Java lead interview questions require a better grasp of technical concepts, they don’t actually assess technical skill. Writing code and using it to define and solve problems can only be assessed in a real-life situation, such as a Java coding task or Java scenario-based coding challenges.
And even then, coding is just a fraction of what makes someone a great engineer.
If you want to test Java technical skills, you could use a code quiz. If you want to assess problem-solving ability, technical collaboration, and Java skills in job-related challenges, you need to use Woven.
Java coding interview questions
Let’s go beyond Java basic interview questions and look at some Java programming interview questions used to test the knowledge of candidates. Below are the first 10 of the Top 100 Java Coding Interview Questions. (Keep in mind that they are Java interview questions for testers, not interviewers.)
- How to reverse a String in Java? Can you write a program without using any Java inbuilt methods?
- Write a Java program to check if two Strings are anagram in Java.
- Write a program to check if String has all unique characters in Java.
- How to check if one String is rotation of another String in Java?
- How to find duplicate characters in String in Java?
- Find first non-repeated character in String in Java?
- Find all substrings of String in Java.
- Find length of String without using any inbuilt method in Java.
- Write a program to print all permutations of String in Java.
- Write Java Program to Find Smallest and Largest Element in an Array.
As you can see, these are Java coding interview questions for experienced professionals. They ask the candidate to complete coding tasks and might be used during a whiteboard interview. But without any software engineer behavioral interview questions, these prompts only scratch the surface of a candidate’s technical skill and ability.
Java interview questions for experienced professionals
With enough Googling, you can find questions to test any level of computer engineering technical knowledge. Many of these lists have advanced Java interview questions for 2 years experience, tricky Java interview questions for 7 years experience, and more. But what if your screening process ignores applicants without specific credentials? Or if you use puzzles that have little resemblance to the actual work the team does?
Java interview questions for freshers 2020
Given the popularity of Java among coding languages and the mega-companies that use it, colleges and universities continue to graduate computer science majors who are ready to begin work using Java coding. Companies screening for entry-level skills have the same choice:
- Use the traditional whiteboard/in-person technical interview to assess candidates with knowledge of Java; or,
- Compile a list of the most popular Java interview questions for freshers and use a code editor.
We know that whiteboard interviews cause anxiety and online code editors don’t paint the whole picture. Plus, Big Tech employs a system of selection that’s optimized for high status individuals with expensive pedigree. If you didn’t go to Stanford, you’re an outsider.
What if there was another way?
Woven’s asynchronous technical assessment platform gives “outsiders” a chance to prove themselves. Every human should be treated with equal value. Therefore, every candidate deserves an experience that’s worthy of experienced engineers.
We also use a network of engineers for evaluation and return individual engineering feedback to each candidate. This feature is especially valuable for freshers. Turns out, the most thorough evaluation process can also be the most candidate friendly.
Java interview questions for 5 years experience
Hiring managers and others involved in recruiting technical talent will find lists of questions and ready-made tests for every Java skill level. There’s an Indeed career guide with 23 Java questions and answers for people with five years of experience, and Guru 99 offers the Top 100 Java Interview Questions and Answers (PDF) in 2021. Software Testing Help provides a more specialized list of “39 TOP automation Questions and Answers.
Java interview questions for 10 years experience 2021
Resources also abound for hiring managers that need senior engineers. Fullstack Café offers a list of 50 Senior Java Developer Questions and Answers, with questions that require an increasing depth of technical knowledge:
- Can == be used on enum?
- Compare the sleep() and wait() methods in Java
- Does Spring Bean provide thread safety?
- How do I read/convert an InputStream into a String in Java?
- What does System.gc() and Runtime.gc() methods do?
- What is JDBC?
- What is reflection and why is it useful?
- What is the function of CI (Continuous Integration) server?
- What is the relationship between a class and an object?
- Is Java “pass-by-reference” or “pass-by-value”?
- Is there anything like static class in java?
- State the features of an interface.
- What are the differences between continuous integration, continuous delivery, and continuous deployment?
Additionally, the Indeed Career Guide provides a list of 35 Tech Lead Interview Questions with Sample Answers and Java Success has 18 Java scenarios based on interview Questions and Answers.
Just for illustration, this is the first scenario:
You need to load stock exchange security codes from a database and cache them for performance. The security codes need to be refreshed every 30 minutes. This cached data needs to be populated and refreshed by a single writer thread and read by several reader threads. How will you ensure that your read/write solution is scalable and thread safe?
Woven’s challenges go beyond Java technical skills
Getting the skill level right in testing is critical. That’s why Woven builds online coding challenges not with technical interview questions, but with role-based job scenarios that assess a candidate’s technical skills. The results, interpreted by our senior engineers, are objective evidence of the candidate’s ability to use code in defining problems, selecting tools, and proposing solutions.
Our report and recommendations give you, the hiring manager, an initial screening of candidates for required technical competencies as well as a foundation that makes Java coding interview questions far more meaningful. Remember: great problem-solvers might not need much code to make a big impact.
Learn more about Woven’s online challenges on our website and start a free trial today. Our professional staff is available to answer questions and to discuss next steps.