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Infosys · Java Developer

Infosys Java Developer Interview Questions (2026): process, questions and answers

Updated 21 October 2026 · prep guide

The Infosys Java Developer interview usually focuses on practical Java basics, Spring Boot, REST APIs, SQL, JVM concepts, and how you think through production issues. Use this page to revise common questions, practise short spoken answers, and connect concepts to enterprise projects such as banking, telecom, or insurance systems.

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How the Infosys Java Developer interview usually works

  1. Resume screening: Candidates commonly report a quick check of project experience, Java stack depth, and whether the resume matches the role. Be ready to explain one or two projects clearly, with your exact contribution.
  2. Technical discussion: This stage usually tests Core Java, collections, threading, Spring Boot, REST, SQL, and JVM basics. Interviewers often move from definitions to practical scenarios, so answer with examples from work or projects.
  3. Coding and problem solving: You may be asked to write simple Java logic, debug code, or explain the output of a snippet. Focus on clean syntax, edge cases, time complexity, and readable code.
  4. Project and domain discussion: Interviewers often ask how your code fits into real business systems, such as payment flow, customer data, batch jobs, or service integrations. Show that you can build reliable, maintainable software, not just write code.
  5. HR and fitment: The final discussion usually checks communication, teamwork, willingness to learn, and comfort with client-facing work. Keep answers honest, structured, and concise.

Technical questions and answers

What is the difference between String, StringBuilder, and StringBuffer in Java?

String is immutable, so every change creates a new object. StringBuilder is mutable and faster for single-threaded string updates. StringBuffer is also mutable, but its methods are synchronized, so it is thread-safe but usually slower. In interviews, say that for repeated concatenation inside loops, StringBuilder is preferred unless multiple threads must access the same object.

How does the final keyword work in Java for variables, methods, and classes?

final means the value or behavior cannot be changed after definition. A final variable cannot be reassigned, though a final reference can still point to a mutable object whose contents change. A final method cannot be overridden, and a final class cannot be extended. Use it when you want safety, readability, and to prevent unintended inheritance or reassignment.

What is the difference between an abstract class and an interface in Java?

An abstract class can hold state, constructors, abstract methods, and concrete methods. An interface mainly defines a contract, and a class can implement multiple interfaces. In modern Java, interfaces can also have default and static methods, but they still do not replace an abstract class when shared state or base implementation is needed. A good answer should mention design intent, not just syntax.

How does HashSet work internally?

HashSet is backed by a HashMap. It stores only unique elements by using the element as a key and a dummy value internally. When you add an object, Java uses hashCode() to find a bucket and equals() to check duplicates within that bucket. The main point to say is that average add, remove, and contains operations are fast, but uniqueness depends on correct object equality logic.

What is fail-fast behavior in Java collections?

Fail-fast means a collection iterator throws ConcurrentModificationException if the collection is structurally modified after the iterator is created, except through the iterator itself. This helps detect unsafe concurrent changes early. It is common in collections like ArrayList and HashMap. In an interview, mention that fail-fast is a safety check, not a concurrency solution, and you should still use proper synchronization where required.

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What is the difference between throw and throws in Java?

throw is used to explicitly raise one exception object inside a method. throws is used in the method signature to declare that the method may pass exceptions to the caller. A simple way to remember it is, throw creates the exception flow, while throws declares it. Also mention that checked exceptions must be handled or declared, while unchecked exceptions do not need declaration.

What is the JVM memory model at a high level?

The JVM typically uses stack memory for method calls and local variables, and heap memory for objects. Each thread has its own stack, while objects created with new live on the heap and are managed by garbage collection. You can also mention method area or metaspace for class metadata. A strong answer connects this to performance issues like memory leaks, OutOfMemoryError, and excessive object creation.

How does garbage collection help in Java, and what should developers still watch for?

Garbage collection automatically removes objects that are no longer reachable, which reduces manual memory management errors. However, it does not solve all memory problems. Developers still need to avoid holding unnecessary references, large caches without limits, and resource leaks like unclosed streams or database connections. A good interview answer should say that GC helps with memory reclamation, but code quality still matters for stable applications.

What is dependency injection in Spring Boot?

Dependency injection means the framework provides an object’s dependencies instead of the class creating them directly. This makes code easier to test, reuse, and maintain. In Spring Boot, you commonly inject dependencies through constructor injection, which is preferred because it makes required dependencies explicit and supports immutability. You can say that DI reduces tight coupling between components.

What is the purpose of HTTP status codes in REST APIs, and which ones are commonly used?

HTTP status codes tell the client what happened with the request. Common examples are 200 OK for success, 201 Created for a new resource, 400 Bad Request for invalid input, 401 Unauthorized for missing or invalid authentication, 404 Not Found when a resource does not exist, and 500 Internal Server Error for unexpected failures. In interviews, mention that correct status codes improve API clarity and client handling.

Scenario questions

A customer API is returning duplicate records when the same request is submitted twice. How would you investigate and fix it?

Start by checking whether the issue is at the API layer, service layer, or database layer. Mention idempotency, request validation, and whether the same payload creates multiple rows because there is no unique constraint or de-duplication key. A strong answer should include logging, transaction review, and database constraints. For a client system, I would also add a request identifier and verify retry handling.

A Spring Boot service is slow during peak usage. What would you look at first?

I would check whether the bottleneck is in the database, external service calls, thread pool limits, or object creation in the Java code. Then I would review logs, response time patterns, SQL query performance, and connection pool settings. If the service is CPU heavy, I would inspect code paths and garbage collection pressure. In an interview, show a step-by-step debugging approach, not guesswork.

In a telecom or banking project, one microservice fails but others keep working. How should the system behave?

Explain that the failure should be isolated. The system should return a clear error, use retries carefully, and avoid cascading failures. You can mention timeouts, circuit breaker style thinking, fallback responses where business allows it, and proper logging for later analysis. The key point is to keep the overall platform stable even if one dependent service is unhealthy.

HR and behavioural questions

Tell me about yourself.

Structure it as present role, strongest skills, relevant projects, and why this role fits. Keep it under two minutes. Sample answer: "I am a Java developer with experience in Core Java, Spring Boot, REST APIs, and SQL. I have worked on enterprise applications where I handled service development, bug fixing, and performance improvements. I enjoy writing clean, maintainable code and working with teams to deliver stable business features."

Tell me about a time you solved a difficult technical problem.

Use the STAR format, situation, task, action, result. Mention the technical issue, what you analysed, the fix, and the impact. Sample answer: "We had a slow API during month-end processing. I checked the query, added the missing index, and reduced unnecessary object creation in the service. The response time improved and the batch window became stable." Keep it factual and measurable if possible.

How do you handle working with a difficult team member or stakeholder?

Show calm communication and focus on delivery. Say you first clarify expectations, listen to the concern, and keep discussions on facts and project goals. Sample answer: "I try to understand the other person’s point of view, explain my reasoning clearly, and align on the requirement or priority. If needed, I involve the lead with data and examples rather than emotion."

Why do you want to join Infosys?

Answer with learning, scale, and client exposure. Sample answer: "I want to join Infosys because it works on large enterprise systems, where I can grow in Java, Spring Boot, and application support across real business domains. I also value the chance to work with structured teams and learn from experienced engineers while contributing to reliable client solutions." Keep it positive and specific, without sounding generic.

Your last 48 hours before the interview

  1. Revise Core Java basics, especially inheritance, abstraction, exceptions, final, and string handling.
  2. Practise explaining collections and JVM concepts aloud in short, clear answers.
  3. Review your most important project, including architecture, your module, database tables, and one production issue you solved.
  4. Write down common Spring Boot, REST, and SQL topics and rehearse one example for each.
  5. Do one or two coding drills with simple Java logic, loops, collections, and edge cases.
  6. Prepare your introduction, reason for change, and one strong example for teamwork or problem solving.

Common mistakes to avoid

Frequently asked questions

What Java topics are most commonly asked in an Infosys interview?

Candidates commonly report questions on Core Java, OOP, collections, multithreading, Spring Boot, REST APIs, SQL, and JVM basics. Interviewers usually want practical understanding, not just definitions. Be ready to explain how you used these topics in a real project.

Does Infosys ask coding questions for Java Developer roles?

Often yes, but the difficulty can vary. You may be asked to write simple Java logic, explain code output, or solve a basic problem with collections or strings. Focus on clear code, edge cases, and explaining your approach aloud.

How should I answer project questions in a Java interview?

Use this pattern, problem, your role, technical approach, result. Mention the business context, the Java or Spring components you used, and what changed because of your work. Keep the answer concrete and avoid vague statements like "I worked on the backend."

What should I revise if I have only one day before the interview?

Prioritise Core Java, collections, exceptions, Spring Boot basics, REST status codes, SQL joins and queries, and JVM memory concepts. Also revise your resume and one or two project stories. Short, accurate answers are better than trying to cover too many topics loosely.

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This is an independent preparation guide based on commonly reported interview patterns. The process varies by team, location and year. Interview AI Helper is not affiliated with Infosys.

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