TCS Java Developer Interview Questions and Answers

API Gateway implementation is a centralized service that routes, manages, and secures API calls.

• API Gateway acts as a single entry point for all API calls

• It can handle authentication, rate limiting, caching, and request/response transformations

• Examples include AWS API Gateway, Apigee, Kong

Circuit breaker is a design pattern used to prevent system overload by temporarily stopping requests to a failing service.

• Circuit breaker monitors requests to a service and opens when the service fails repeatedly.

• It helps prevent cascading failures and allows the system to gracefully degrade.

• Once the circuit breaker is open, it can periodically check if the service has recovered before allowing requests again.

Deadlock is a situation in which two or more processes are unable to proceed because each is waiting for the other to release a resource.

• Avoid circular wait by ensuring processes request resources in the same order.

• Prevent hold and wait by requiring processes to request all needed resources at once.

• Implement a timeout mechanism to break potential deadlocks.

• Use resource allocation graphs to detect and prevent deadlocks.

• ...read more

The equals() method is used to compare the contents of two objects for equality.

• The equals() method is a method of the Object class in Java.

• It is used to compare the contents of two objects for equality.

• The default implementation of equals() in the Object class compares memory addresses, so it is often overridden in custom classes to compare content.

• Example: String class overrides equals() method to compare the content...read more

MongoDB was integrated in the application by using the official Java driver and configuring connection settings.

• Used the official MongoDB Java driver to interact with the database

• Configured connection settings such as host, port, database name, and authentication credentials

• Implemented CRUD operations using MongoDB Java driver methods

• Utilized MongoDB aggregation framework for complex queries

Hibernate is an object-relational mapping (ORM) framework for Java that simplifies database interactions.

• Hibernate maps Java classes to database tables, allowing developers to work with Java objects instead of SQL queries.

• It provides a powerful query language called HQL (Hibernate Query Language) that is similar to SQL but operates on objects.

• Hibernate supports various database systems, making it versatile for differen...read more

Runnable is a functional interface with a single run() method, while Callable is a functional interface with a single call() method.

• Runnable is used for tasks that do not return a result, while Callable is used for tasks that return a result.

• Callable can throw checked exceptions, while Runnable cannot.

• Callable returns a Future object, which can be used to retrieve the result of the computation.

• Example: Runnable - execu...read more

The Callable interface in Java returns a Future object.

• Callable interface returns a Future object which represents the result of a computation that may not be available yet.

• The Future object can be used to retrieve the result of the computation, check if it is done, or cancel the computation.

• Example: Callable<Integer> task = () -> { return 42; }

ConcurrentHashMap allows concurrent access and updates, ensuring thread safety without locking the entire map.

• Uses a segmented locking mechanism to allow multiple threads to read and write concurrently.

• Divides the map into segments, each with its own lock, reducing contention.

• Supports operations like put, get, and remove without blocking the entire map.

• Example: Inserting elements in a multi-threaded environment allows ...read more

Monitor application health using metrics, logs, alerts, and performance monitoring tools.

• Use monitoring tools like Prometheus, Grafana, or New Relic to track key metrics such as CPU usage, memory usage, response times, and error rates.

• Implement logging to record important events and errors in your application. Use tools like ELK stack (Elasticsearch, Logstash, Kibana) for log analysis.

• Set up alerts to notify you of any...read more

To call an API in a Microservice architecture, use HTTP requests or messaging protocols like gRPC.

• Use HTTP requests to communicate between microservices

• Implement RESTful APIs for easy integration

• Leverage messaging protocols like gRPC for efficient communication

• Consider using service discovery mechanisms for dynamic API calls

Profiles in Java are configurations that define the capabilities of a Java platform.

• Profiles allow developers to target specific types of devices or applications.

• They help in reducing the size of the Java runtime environment by including only the necessary APIs.

• Examples include Java SE Embedded Profile for embedded devices and Java SE Compact Profile for resource-constrained environments.

OpenFeign is a declarative web service client used to simplify the process of making HTTP requests in microservices architecture.

• OpenFeign allows developers to define RESTful web services as interfaces and automatically generate the necessary implementation code.

• It integrates seamlessly with Spring Cloud and other microservices frameworks to facilitate communication between services.

• OpenFeign supports features like loa...read more

Service registry and discovery involves registering services and allowing clients to discover and connect to them.

• Implement a service registry where services can register themselves with metadata

• Use a service discovery mechanism for clients to find and connect to services

• Implement health checks to ensure services are available and healthy

• Use a load balancer to distribute traffic among multiple instances of a service

Spring Boot Actuators are built-in tools that provide insight into the running application.

• Actuators expose various endpoints to monitor and manage the application.

• They can be used to check health, metrics, environment details, and more.

• Examples include /actuator/health, /actuator/metrics, and /actuator/env.

Synchronous communication is blocking, while asynchronous communication is non-blocking.

• Synchronous communication waits for a response before continuing, while asynchronous communication does not wait.

• Examples of synchronous communication include traditional function calls, while examples of asynchronous communication include callbacks and promises.

• Synchronous communication can lead to performance issues if there are d...read more

Synchronized keyword is used in Java to control access to shared resources by multiple threads.

• Synchronized keyword can be applied to methods or code blocks to ensure only one thread can access the synchronized code at a time.

• It prevents race conditions and ensures thread safety by creating a lock on the object or class.

• Example: synchronized void myMethod() { // synchronized code block }

Excessive use of synchronized blocks and methods in Java can lead to performance issues and potential deadlocks.

• Decreased performance due to increased contention for locks

• Potential deadlocks if multiple threads are waiting for each other to release locks

• Increased complexity and difficulty in debugging and maintaining code

• Use synchronized sparingly and consider alternatives like ConcurrentHashMap or Lock interface

The number of threads needed for an application can be determined based on factors like the type of tasks, hardware resources, and performance requirements.

• Consider the type of tasks your application needs to perform - CPU-bound tasks may benefit from more threads, while I/O-bound tasks may not.

• Take into account the hardware resources available - more threads may be beneficial on a multi-core processor compared to a si...read more

Executor framework is a framework in Java that provides a way to manage and execute tasks asynchronously.

• Allows for managing thread execution in a more efficient way

• Provides a way to decouple task submission from task execution

• Supports various types of executors like ThreadPoolExecutor and ScheduledExecutorService

• Helps in handling tasks concurrently and asynchronously

BlockingQueue is an interface in Java that represents a queue which supports operations that wait for the queue to become non-empty when retrieving an element and wait for space to become available in the queue when adding an element.

• BlockingQueue is part of the java.util.concurrent package.

• It is used for implementing producer-consumer scenarios where multiple threads are involved.

• Methods like put() and take() are used...read more

Seeking new challenges and opportunities for growth.

• Desire for career advancement

• Looking for new challenges

• Seeking better work-life balance

• Company restructuring or downsizing

• Relocation to a new area

Unit testing in Java ensures code reliability and helps catch bugs early in the development process.

• Use JUnit framework for writing unit tests. Example: @Test annotation for test methods.

• Mock dependencies using Mockito to isolate the unit being tested. Example: Mockito.when(...).thenReturn(...).

• Follow the Arrange-Act-Assert pattern for structuring tests. Example: Arrange inputs, Act by calling the method, Assert the ex...read more