CSS Corp Java Developer Interview: Rounds, Questions and Preparation

What the job involves

As a Java Developer at Indian IT services companies like CSS Corp, you will build and maintain web applications and backend services using Java, Spring, and SQL. Day to day work includes writing code, fixing bugs, attending standups, and coordinating with senior developers and QA teams. You may also support production issues and learn client-specific frameworks on the job.

Role and Technical Knowledge

1. 1

   What is the difference between an abstract class and an interface in Java, and when would you use each?

   Explain that abstract classes can have constructors and state, while interfaces define a contract. Mention that Java 8+ allows default methods in interfaces. Give a practical example like using an interface for service contracts and an abstract class for shared base logic.

2. 2

   Explain the Java collections framework. Which collection would you use for frequent insertions and deletions from the middle of a list?

   Cover List, Set, Map, and their common implementations. For middle insertions and deletions, LinkedList is better than ArrayList because it does not require shifting elements. Mention that in practice ArrayList is often preferred unless you specifically need frequent middle operations.

3. 3

   How does Spring Boot help in building REST APIs? What annotations have you used?

   Mention @RestController, @RequestMapping, @GetMapping, @PostMapping, @RequestBody, and @PathVariable. Explain that Spring Boot reduces boilerplate with auto-configuration and embedded servers. If you have not used it, say you have learned it through projects and describe a simple CRUD API you built.

4. 4

   Write a SQL query to find the second highest salary from an Employee table.

   Show a query using a subquery or LIMIT/OFFSET. For example: SELECT MAX(salary) FROM Employee WHERE salary < (SELECT MAX(salary) FROM Employee); or SELECT salary FROM Employee ORDER BY salary DESC LIMIT 1 OFFSET 1; Explain the logic clearly.

Practical Scenarios

1. 5

   You are asked to fix a bug in a Java web application that only happens in production, not in your local environment. How do you approach it?

   Talk about checking logs, reproducing the issue with production-like data, comparing configurations, and using debugging or remote logging. Mention communicating with the team and not making changes directly in production without approval.

2. 6

   A client wants a small feature added to an existing Spring Boot application. How would you plan and implement it?

   Describe understanding the requirement, checking existing code structure, writing the controller, service, and repository layers, adding unit tests, and testing locally before raising a pull request. Mention following the team's coding standards and Git workflow.

3. 7

   Your code passes all unit tests but fails during integration testing with the database. What could be wrong and how do you debug it?

   Suggest checking database connection settings, transaction management, SQL dialect differences, and data setup. Mention using logs, checking the exact SQL generated, and verifying that test data exists. Also mention isolating the failing layer.

4. 8

   You are asked to optimize a slow-performing SQL query used by a Java application. What steps would you take?

   Talk about using EXPLAIN PLAN, checking indexes, avoiding SELECT *, reducing joins, and adding pagination. Mention testing the query directly in the database and then measuring improvement in the application.

Behavioural and HR Questions

1. 9

   Tell me about a time you had to learn a new technology quickly for a project or assignment.

   Use the STAR method. Describe the situation, what you needed to learn, how you learned it (online resources, documentation, practice), and the result. Show that you are self-driven and can pick up new skills.

2. 10

   How do you handle it when you are stuck on a coding problem for a long time?

   Mention that you first debug systematically, search documentation or forums, and then ask for help if needed. Emphasize that you do not give up easily but also know when to escalate. Give a small example if possible.

3. 11

   Are you willing to relocate or work in different shifts as required by the project?

   Be honest but positive. If you are flexible, say yes and explain that you see it as an opportunity. If you have constraints, state them politely and show willingness to adjust where possible. Indian IT services often require shift flexibility.

4. 12

   Why do you want to join a company like CSS Corp as a Java Developer?

   Research the company's services and clients. Talk about wanting to work on real-world Java projects, learn from experienced teams, and grow in a services environment. Avoid generic answers like 'good company' and connect your skills to the role.

Coding and Problem Solving

1. 13

   Write a Java program to check if a given string is a palindrome.

   Show a simple approach using two pointers or StringBuilder reverse. Handle edge cases like null, empty string, and case sensitivity. Explain the time complexity, which is O(n).

2. 14

   Given an array of integers, find the pair that sums to a given target. Write the logic in Java.

   Use a HashMap to store numbers and check for target minus current element. This gives O(n) time. Mention that a brute-force nested loop is O(n^2) and less efficient. Explain your code clearly.

3. 15

   How would you remove duplicate elements from an ArrayList in Java?

   Use a LinkedHashSet to preserve order, or use Java 8 streams with distinct(). Explain that Set does not allow duplicates. Show a small code snippet and mention that this is a common utility task.

4. 16

   Write a Java method to reverse a linked list.

   Explain the iterative approach using three pointers: previous, current, and next. Walk through the steps. Mention that recursion is also possible but uses stack space. This tests your understanding of data structures.