Mindtickle India Java Developer Interview: Rounds, Questions and Preparation

What the job involves

Java Developers at Indian IT services companies build, test, and maintain backend components of enterprise applications, often working in Agile teams for clients across BFSI, retail, or SaaS. Freshers typically start with bug fixes, small feature development, and writing unit tests under the guidance of a senior developer. The role demands solid Java and Spring fundamentals, basic database skills, and comfort with version control and debugging.

Java and OOP Fundamentals

1. 1

   Explain the difference between an interface and an abstract class in Java, and when you would use each in a service-based project.

   Cover multiple inheritance of type via interfaces, default methods, and abstract class use for shared state or partial implementation. Relate to real code you wrote.

2. 2

   How does HashMap work internally in Java 8 and later?

   Explain hashing, buckets, equals and hashCode contract, collision handling with linked lists, and treeification when bucket size exceeds 8. Mention initial capacity and load factor.

3. 3

   What is the difference between checked and unchecked exceptions? Give an example of when you would create a custom exception.

   Define both, note that checked exceptions must be declared or handled, and give a business example like InvalidOrderException. Show you know try-with-resources.

4. 4

   Write a Java program to reverse a string without using StringBuilder or StringBuffer.

   Use a char array and swap from both ends, or build a new string with a loop. Explain time and space complexity and handle null or empty input.

Spring Boot, REST, and Databases

1. 5

   What is dependency injection in Spring, and how does @Autowired work?

   Explain inversion of control, constructor vs field injection, and why constructor injection is preferred. Mention the Spring container and bean lifecycle briefly.

2. 6

   How would you design a REST API for a simple employee management system? List the endpoints and HTTP methods.

   Cover resource naming, GET, POST, PUT, DELETE, status codes like 200, 201, 404, and 400. Mention request and response JSON structure.

3. 7

   Given two tables, Employee and Department, write a SQL query to find the second highest salary in each department.

   Use a correlated subquery or window function like DENSE_RANK. Explain how you would test the query with sample data.

4. 8

   What is the difference between @RestController and @Controller in Spring Boot?

   Explain that @RestController combines @Controller and @ResponseBody, so methods return data not view names. Mention when you would use a traditional controller with a templating engine.

Practical Scenarios and Project Work

1. 9

   You are asked to fix a bug where an API returns 500 for certain inputs. Walk me through how you would debug it.

   Start with logs, reproduce the issue, check input validation, trace the stack trace, and isolate the failing layer. Mention using a debugger or adding temporary logs.

2. 10

   Your project uses Maven and the build fails on a teammate's machine but works on yours. What do you check?

   Check Java version, Maven version, local repository, dependency scope, and environment variables. Suggest using a wrapper or Docker to standardise the build.

3. 11

   Describe a time you had to learn a new technology quickly for a college project or internship. How did you approach it?

   Use the STAR method. Focus on a specific technology, the resources you used, and the outcome. Show a structured learning approach.

4. 12

   How would you write a unit test for a method that calculates the total price of items in a shopping cart?

   Mention JUnit, test cases for empty cart, single item, multiple items, discounts, and invalid inputs. Explain assertions and why you mock external dependencies.

Behavioural and HR Questions for Freshers

1. 13

   Why do you want to join a service-based IT company rather than a product company?

   Show awareness of client projects, diverse domain exposure, structured training, and opportunities to work across technologies. Be honest and positive.

2. 14

   You are assigned to a project using a framework you have never used. How do you handle it?

   Emphasise self-learning, documentation, asking mentors, and breaking the task into smaller parts. Give an example of a time you learned something new.

3. 15

   Tell me about a time you disagreed with a team member during a college project. How did you resolve it?

   Use STAR. Focus on listening, discussing with data or logic, and reaching a consensus. Show you can disagree without being disagreeable.

4. 16

   Where do you see yourself in three years in this role?

   Align with growing into a reliable developer, mastering the tech stack, contributing to design, and possibly mentoring juniors. Avoid saying you want to leave for higher studies immediately.