Junior Java Developer Interview Questions

3,831 junior java developer interview questions shared by candidates

🧠 The process included 3 technical rounds (excluding HR) — all focused on Java, DSA, system design fundamentals, and real-time problem-solving. 🔹 Round 1 – Core Java + DSA + SQL DSA Problem: Find the maximum product of a triplet in an array 👉 Input: 1, 4, 7, 9, -2, 10 → Output: 630 👉 Input: -4, -5, 0, 2, 3, 9 → Output: 180 Java Questions: 👉 What is the Collection Framework in Java? 👉 Difference between List, Set, and Queue 👉 JVM vs JRE vs JDK 👉 Java 8 features (Lambda Expressions, Default & Static methods, etc.) 👉 Code Binary Search + Time Complexity SQL: Write a query to fetch the 3rd highest salary from an Employee table. 🔹 Round 2 – DSA + Java Internals + Culture Fit LeetCode Problems: 1. Longest Substring Without Repeating Characters – also asked to print it and analyze time complexity. 2. Balanced Parentheses – Solved with a space-optimized approach (without using stack). Interviewer appreciated the use of O(1) space. Java Questions: 👉 Iterable vs Collection interfaces 👉 How HashMap works (Asked again) 👉 Multithreading concepts 👉 Memory Management and Garbage Collector in Java Also discussed some Linux commands and had a light conversation about my college life in NIT Agartala, the culture of Tripura, and local languages. 🔹 Round 3 – Managerial + Conceptual Discussion Coding: Write code for generating the Fibonacci Series 👉 Java OOPs Concepts: 👉 Constructor vs Interface 👉ArrayList vs LinkedList Other Topics: 👉 Basics of REST API 👉 Introduction to Spring Boot 👉 Real-world backend scenarios 👉 Role expectations and cultural questions 💬 Overall, the experience was enriching. The interviewers were friendly and genuinely curious about both my technical skills and personality. 💡 Advice to fellow developers preparing for backend interviews: 👉 Master core Java + OOPs + Java 8 features 👉 Practice DSA (LeetCode/Easy–Medium level) 👉 Be ready to explain your approach, optimize, and discuss trade-offs 👉 Understand Collection Framework, Multithreading, and Memory Management 👉 Revisit SQL basics and REST API fundamentals
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Junior Java Developer

Interviewed at Nextiva

3.6
Apr 21, 2025

🧠 The process included 3 technical rounds (excluding HR) — all focused on Java, DSA, system design fundamentals, and real-time problem-solving. 🔹 Round 1 – Core Java + DSA + SQL DSA Problem: Find the maximum product of a triplet in an array 👉 Input: 1, 4, 7, 9, -2, 10 → Output: 630 👉 Input: -4, -5, 0, 2, 3, 9 → Output: 180 Java Questions: 👉 What is the Collection Framework in Java? 👉 Difference between List, Set, and Queue 👉 JVM vs JRE vs JDK 👉 Java 8 features (Lambda Expressions, Default & Static methods, etc.) 👉 Code Binary Search + Time Complexity SQL: Write a query to fetch the 3rd highest salary from an Employee table. 🔹 Round 2 – DSA + Java Internals + Culture Fit LeetCode Problems: 1. Longest Substring Without Repeating Characters – also asked to print it and analyze time complexity. 2. Balanced Parentheses – Solved with a space-optimized approach (without using stack). Interviewer appreciated the use of O(1) space. Java Questions: 👉 Iterable vs Collection interfaces 👉 How HashMap works (Asked again) 👉 Multithreading concepts 👉 Memory Management and Garbage Collector in Java Also discussed some Linux commands and had a light conversation about my college life in NIT Agartala, the culture of Tripura, and local languages. 🔹 Round 3 – Managerial + Conceptual Discussion Coding: Write code for generating the Fibonacci Series 👉 Java OOPs Concepts: 👉 Constructor vs Interface 👉ArrayList vs LinkedList Other Topics: 👉 Basics of REST API 👉 Introduction to Spring Boot 👉 Real-world backend scenarios 👉 Role expectations and cultural questions 💬 Overall, the experience was enriching. The interviewers were friendly and genuinely curious about both my technical skills and personality. 💡 Advice to fellow developers preparing for backend interviews: 👉 Master core Java + OOPs + Java 8 features 👉 Practice DSA (LeetCode/Easy–Medium level) 👉 Be ready to explain your approach, optimize, and discuss trade-offs 👉 Understand Collection Framework, Multithreading, and Memory Management 👉 Revisit SQL basics and REST API fundamentals

I said my project was in Servlet and JDBC. 1. Lifecycle of Servlet. 2. Which Collection did you use in project. 3. Thread Executer Pool. 4. Future Class in Java. 5. Difference between Final, Finally and Finalize. 6. Deamon Thread. 7. Garbage Collector.
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Junior Java Developer

Interviewed at Morningstar

3.8
Sep 16, 2021

I said my project was in Servlet and JDBC. 1. Lifecycle of Servlet. 2. Which Collection did you use in project. 3. Thread Executer Pool. 4. Future Class in Java. 5. Difference between Final, Finally and Finalize. 6. Deamon Thread. 7. Garbage Collector.

They asked me several technical questions related to my project implementation, such as: How I linked the Java Spring Boot application with the SQL database. How the data from a JSON file was being parsed and processed. Which OOP principles I applied in a specific code snippet, and why (for example, the use of abstraction and its necessity).
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Junior Java Developer

Interviewed at Securin

3.2
Aug 23, 2025

They asked me several technical questions related to my project implementation, such as: How I linked the Java Spring Boot application with the SQL database. How the data from a JSON file was being parsed and processed. Which OOP principles I applied in a specific code snippet, and why (for example, the use of abstraction and its necessity).

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