Top 30 Java Interview Questions for Testers

A career in Java testing is sure to be a rewarding one if you’re working for a FAANG+ company. As a Java tester, your primary role is to test Java/J2EE applications during the development cycle. Java interview questions for testers mostly revolve around programming theory and coding. As testers are also involved with the overall performance of applications, Java testing interview questions around systems design also feature in technical interviews. 

In this piece, we’ll look at some popular Java interview questions for testers. We’ll first look at some Java interview questions and answers for experienced testers, followed by general programming- and design-related questions. 

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Let’s go ahead and look at some Java interview questions and answers for experienced testers, along with popular sample Java interview questions for testers. These questions will help you form a concrete idea of the type of questions asked in technical interviews at FAANG+ companies. 

Here’s what we’ll cover in this article:

• Popular Java Interview Questions and Answers for Experienced Testers
• Java Coding Interview Questions for Testers
• Java Systems Design Interview Questions for Testers
• FAQs on Java Interview Questions for Testers
  

Popular Java Interview Questions and Answers for Experienced Testers

In this section, we’ll look at some popular Java interview questions and answers for experienced testers.

Q1. What OOPs concepts are important while performing manual testing of Java applications?

This is one of the most common Java interview questions for testers. OOPs is an important programming paradigm that is applicable to testing applications in JavaScript and J2EE. The important OOPs concepts applicable in testing include - Abstraction, Encapsulation, Polymorphism, Inheritance, Method Overriding, Method Overloading, and Data Binding. 

Q2. What are some tools used in testing applications built using Java frameworks?

Some popular Java testing tools used to test applications coded in the language include:

• JBehave
• JUnit
• Serenity
• Selenium
• Gauge 
• Mockito

Q3. What are some advantages of employing Java test automation frameworks?

This is one of the most popular Java interview questions for testers. The main advantages of using Java test automation frameworks include:

• Test automation frameworks help to carry out the testing process seamlessly by improving speed and accuracy
• Automation testing allows for code reusability, a core feature necessary while testing J2EE applications. 
• Test reports can be retrieved automatically after test cases are executed. 

Q4. Which are the different types of test automation frameworks for testing applications?

This is a common Java interview question for testers asked in technical interviews. The main types of test automation frameworks for testing applications coded in Java are:

• Keyword-Driven Testing Frameworks
• Hybrid Testing Frameworks
• Data-Driven Testing Frameworks
• Modular Testing Frameworks

Q5. What type of test cases are mostly required to be automated?

This is one of the most popular Java interview questions for testers. Test cases that require to be automated include:

• Sanity Test Cases
• Smoke Test Cases
• Regression Test Cases

Java Coding Interview Questions for Testers

Java interview questions for testers include questions in coding concepts, mostly those pertaining to core data structures and algorithms. Coding is an important part of testing interviews. The main topics that feature in Java interview questions for testers at coding interviews:

• Arrays, strings, and linked lists
• Sorting algorithms — quicksort, merge sort, heap sort, etc.
• Hash tables and queues
• Recursion
• Trees and graphs
• Graph algorithms, including greedy algorithms
• Dynamic programming
  

Let’s go ahead and look at some popular Java interview questions for testers in coding:

1. For a given array of size N, write a code to print the reverse of the array
2. For a given array A, write a code to delete the duplicate elements in the array
3. For a given array Arr[] containing integer elements, write a code to find the minimum and maximum elements of the array
4. For a given array of size N containing distinct integer numbers, write a code to sort the array in the wave fashion
5. From a given array containing integer values, write a code to find the maximum subarray of non-negative numbers
6. For a given String S, write a program to remove duplicate elements from the String
7. For a given String S, write a code to find the minimum number of elements or characters that need to be inserted to convert it into a palindrome
8. For a given String S, write a program to find the length of the longest Substring with distinct values
9. For a given String S, write a code to remove successive duplicate characters recursively
10. For two strings, A and B, write a program to figure out if B can be obtained by rotating A in at least two places
11. Write a code to add two numbers represented by Linked Lists
12. Write a function to remove the nth node from a Linked List
13. Write a program to swap adjacent nodes in a Linked List
14. Write a code to reverse a Linked List from position X to position Y
15. For a given Linked List, write a code to return the node value where the cycle in question begins
16. For a given binary tree, write a function to connect nodes that are at the same level
17. For a given binary tree T, write a function to find its spiral order traversal
18. For a given binary tree, write a program that traces its vertical traversal
19. For a given binary tree T, write a code to print the bottom view of the tree from left to right
20. You're given the root of a binary tree T. Write a program to find out of it is a Binary Search Tree or not

Java Systems Design Interview Questions for Testers

Systems design is an important part of testing interviews. Java interview questions for testers consist of questions in distributed systems design, mostly asked at on-site interviews. 

Let’s go ahead and look at some popular Java interview questions for testers in distributed systems design. 

Before that, here are the essential topics to prepare for the design interview:

• Basics of Systems Design
• Caching
• Storage and retrieval
• MapReduce and distributed file systems
• Concurrency 
• Basics of API modeling 
• Network protocols
• Scalable systems and scaling applications
• Replication
• Sharding techniques
• Measuring the performance of scalable systems
  

Below are some sample Java interview questions for testers in distributed systems design.

1. How would you design a file-sharing service like Dropbox?
2. What is your approach to designing a cloud communications system?
3. How would you design a chatbot service?
4. How would you ensure that your system is secure to end-users?
5. How would you design a system like Instagram?
6. What factors would you account for while designing an e-commerce system?
7. What is your approach to designing a cab-hailing service?
   

Practicing such Java interview questions for testers is key to preparing for and cracking your next Java Testing interview. Include these questions in your prep, and you will surely see results. All the best!

FAQs on Java Interview Questions for Testers

Q1. What is the interview process in general for Java testers are FAANG+ companies?

The interview process for Java testers involves a Technical Phone Screen Round and an On-site interview round comprising coding and design rounds. 

Q2. What type of Java interview questions for testers are asked in coding interviews?

Java interview questions for testers are mostly around programming theory, automation frameworks, testing test cases, testing tools, coding, problem-solving, and distributed systems design.

Q3. Which are the two fundamental ways to carry out application testing using Java?

The two most common ways to carry out application testing are Functional Testing and Non-Functional Testing. 

Q4. Are behavioral interview questions part of Java interview questions for testers at FAANG+ interviews?

Behavioral questions are an essential part of interviews for testers. You can expect behavioral interview questions during on-site interviews. Questions are primarily around leadership, cooperation, integrity, ethics, and work-life balance. 

Q5. Which are the important coding concepts to prepare for testing interviews?

Java interview questions for testers consist of problems in coding. Your problem-solving is fundamentally tested through your ability to solve problems around core data structures and algorithms. The important coding concepts include - Arrays, Strings, Linked Lists, Recursion, Hash Tables, Dynamic Programming, Trees, Graphs, and Greedy Algorithms.

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