TCS Java Developer Interview Questions, Process, and Tips

Java is a programming language while Hibernate is an ORM tool for Java.

• Java is an object-oriented language used for developing applications.

• Hibernate is an ORM tool that simplifies database access for Java applications.

• Hibernate maps Java classes to database tables and provides a framework for querying and manipulating data.

• Hibernate reduces the amount of boilerplate code needed for database access in Java applications

OOPs is a programming paradigm based on the concept of objects.

• OOPs stands for Object-Oriented Programming.

• It focuses on creating objects that contain both data and functions.

• Encapsulation, Inheritance, and Polymorphism are the three main pillars of OOPs.

• Java, C++, Python, and Ruby are some of the popular OOPs languages.

• Example: A car can be an object with properties like color, model, and functions like start, stop, a

Java 8 introduced several new features including lambda expressions, streams, and functional interfaces.

• Lambda expressions allow for functional programming and simplify code.

• Streams provide a way to process collections of data in a declarative way.

• Functional interfaces enable the use of lambda expressions and method references.

• Default methods allow for adding new methods to interfaces without breaking existing implemen...read more

Array is a fixed size data structure while ArrayList is a dynamic size data structure in Java.

• Array is a primitive data type while ArrayList is a class in Java.

• Array can hold only homogeneous data types while ArrayList can hold heterogeneous data types.

• Array needs to be initialized with a fixed size while ArrayList can be initialized without a size.

• Array uses [] brackets to declare while ArrayList uses <> brackets to d...read more

Collection framework is a set of classes and interfaces that provide a way to store and manipulate groups of objects.

• It includes interfaces like List, Set, and Map

• It provides implementations like ArrayList, HashSet, and HashMap

• It simplifies the process of storing and manipulating data

• It allows for easy iteration and sorting of collections

• Example: List names = new ArrayList<>();

• Example: Map ages = new H

Marker interface is an interface with no methods, used to mark a class as having a certain property or behavior.

• Marker interfaces are used for metadata purposes.

• They are used to provide information to the compiler or runtime environment.

• Examples of marker interfaces in Java include Serializable, Cloneable, and Remote.

• Marker interfaces can also be used to enforce design patterns, such as the Decorator pattern.

Thread is a lightweight sub-process, a separate path of execution within a program.

• Threads allow concurrent execution of two or more parts of a program.

• Java provides built-in support for multithreading through the Thread class and Runnable interface.

• Threads can be created by extending the Thread class or implementing the Runnable interface.

• Thread.sleep() method is used to pause the execution of a thread for a specified...read more

JDBC is a low-level API for connecting to databases, while Hibernate is a high-level ORM framework.

• JDBC requires manual coding for CRUD operations, while Hibernate provides automatic mapping of objects to database tables.

• JDBC is more suitable for small-scale applications, while Hibernate is better for large-scale applications.

• Hibernate provides caching and lazy loading, which improves performance, while JDBC does not h...read more

String buffer is synchronized while string builder is not.

• String buffer is thread-safe while string builder is not.

• String buffer is slower than string builder.

• String builder is preferred for single-threaded operations.

• Both classes are used for manipulating strings.

• Example: StringBuffer sb = new StringBuffer(); StringBuilder sb = new StringBuilder();

Microservices is an architectural style that structures an application as a collection of small, independent services.

• Microservices are independently deployable and scalable.

• Each microservice focuses on a specific business capability.

• Communication between microservices is usually done through APIs.

• Microservices can be developed using different programming languages and technologies.

• Examples of companies using microserv

Constructor chaining is calling one constructor from another constructor within the same class.

• It allows to reuse the code of one constructor in another constructor.

• It is achieved using the 'this' keyword followed by the constructor parameters.

• It can be used to set default values or to initialize variables before calling another constructor.

• Example: public MyClass(int x) { this(x, 0); } public MyClass(int x, int y) { t

Exception handling is a mechanism to handle runtime errors. There are two types of exceptions: checked and unchecked.

• Checked exceptions are checked at compile-time and must be handled or declared in the method signature.

• Unchecked exceptions are not checked at compile-time and can be handled using try-catch or thrown to the calling method.

• Common exceptions include NullPointerException, ArrayIndexOutOfBoundsException, an...read more

HTTP servlet is a Java class that extends the capabilities of servers that host applications accessed by HTTP protocol.

• HTTP servlet is a Java class that extends the capabilities of servers that host applications accessed by HTTP protocol

• It is used to handle HTTP requests and responses

• It provides methods to get information about the request and to send a response back to the client

• It can be used to create dynamic web pa...read more

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

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 open-source Java framework that simplifies the development of database interactions in Java applications.

• Hibernate is an Object-Relational Mapping (ORM) tool that maps Java objects to database tables.

• It provides a way to perform database operations using Java objects instead of writing SQL queries.

• Hibernate handles the mapping of Java classes to database tables and vice versa, as well as the generation ...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; }

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

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