TCS Java Interview | Java | Spring Boot | Microservices | Database

TCS Java Interview | Java | Spring Boot | Microservices | Database

This post is based on a Java backend developer interview simulation and provides direct transcript-based answers to help you prepare for similar interviews.

📺 This interview scenario was inspired by a video from the YouTube channel: CloudTech.
🔗 Watch the full video here: https://www.youtube.com/watch?v=yVj2EgwZxk4

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1. Can you introduce yourself and talk about your tech stack and domains?

I have around 4.5 years of experience working as a Java developer. My core expertise is in Java and developing REST APIs using Spring Boot. I also have basic knowledge of microservices architecture. On the database side, I work with SQL and Oracle. Additionally, I have exposure to UI technologies like Angular, HTML, and CSS, but they are secondary skills. My primary focus is backend Java development.

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2. Which version of Java are you currently working on?

We are currently using Java 8 but are in the process of upgrading to Java 17.

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3. How would you rate yourself in Core Java out of 5?

I would rate myself a 4 out of 5 in Core Java.

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4. What are the different ways to create threads in Java?

Threads can be created in three ways:

• By extending the Thread class and overriding the run() method.

• By implementing the Runnable interface and providing the implementation for run().

• By using the Executor framework which manages a pool of threads.

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5. What is the recommended way to create threads?

• For multiple threads: use the Executor framework.

• For a single thread and if the class is not extending any other class: extend Thread.

• In general, it's best to implement Runnable.

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6. What is a deadlock and how can we avoid it?

Deadlock occurs when two or more threads are waiting on each other’s resources. For example, Thread 1 holds Resource A and waits for Resource B, while Thread 2 holds Resource B and waits for Resource A.
To avoid deadlock:

• Use locks in a consistent order.

• Use tryLock() from java.util.concurrent.locks.

• Minimize synchronized blocks.

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7. What are the thread states in Java?

• New: Thread is created but not started.

• Runnable: Thread is ready to run.

• Blocked/Waiting/Timed Waiting: Thread is waiting to acquire a lock or a specific time.

• Terminated: Thread has finished execution.

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8. Can a terminated thread be restarted?

No, once a thread is terminated, it cannot be restarted. You can only create a new thread.

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9. Difference between throw and throws?

• throw is used to explicitly throw an exception in the code.

• throws is used in the method signature to indicate it may throw exceptions.

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10. Types of exceptions in Java?

• Checked exceptions: Checked at compile-time (e.g., IOException).

• Unchecked exceptions: Runtime exceptions (e.g., NullPointerException, ArrayIndexOutOfBoundsException).

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11. What is try-with-resources?

A try-with-resources block allows us to declare resources like BufferedReader with the try block. The resource is automatically closed after execution. The resource must implement AutoCloseable.

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12. Difference between == and .equals()?

• == compares object references.

• .equals() compares the content of objects.

Example:

String s1 = "abc";
String s2 = new String("abc");
s1 == s2 // false
s1.equals(s2) // true

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13. Difference between abstract class and interface?

• Abstract class can have both abstract and concrete methods.

• Interface can have abstract methods, and from Java 8 onwards, also static and default methods.

• A class can extend only one abstract class but can implement multiple interfaces.

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14. What is Dependency Injection and how does Spring Boot support it?

Dependency Injection is a design pattern where dependencies are injected rather than created. Spring Boot supports it using annotations like @Autowired or @Bean.

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15. What is circular dependency and how does Spring handle it?

Spring handles circular dependencies using proxy objects or by using @Lazy annotation to lazily load dependencies. Best practice is to refactor code to avoid circular dependencies.

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16. Difference between CrudRepository and JpaRepository?

• CrudRepository: Basic CRUD operations.

• JpaRepository: Extends CrudRepository and provides extra features like pagination and sorting.

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17. What kind of repository do you use in your project?

We use JpaRepository because it supports pagination and other features.

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18. Best practices to improve Spring Boot performance?

• Use caching to avoid frequent DB calls.

• Apply proper indexing in DB.

• Use Spring Boot Actuator for monitoring.

• Use @Async for asynchronous processing.

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19. How to convert a monolithic application to microservices?

• Analyze and identify domain boundaries.

• Break the application into independent services.

• Use REST for synchronous communication, and Kafka/RabbitMQ for asynchronous.

• Add API Gateway.

• Use Service Discovery.

• Apply CI/CD with Docker and Kubernetes.

• Implement unit and regression testing.

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20. Difference between synchronous and asynchronous communication in microservices?

• Synchronous: Client sends request and waits (e.g., REST APIs).

• Asynchronous: Client sends message and continues (e.g., Kafka, RabbitMQ).

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21. Java 8 Program: Unique Words from Sentence

public class Client {
    public static void main(String[] args) {
        String str = "Java is fun and Java is powerful";
        List<String> uniqueWords = Arrays.stream(str.split(" "))
            .map(String::toLowerCase)
            .distinct()
            .sorted()
            .collect(Collectors.toList());
        System.out.println(uniqueWords);
    }
}

Output: [and, fun, is, java, powerful]

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📌 Conclusion

👉 If you found this useful, explore our other posts on:

• Java Interview Questions

• Spring Boot Real-World Scenarios

• Microservices Implementation Guide

💬 Got any questions or tips to share? Drop them in the comments!