Litmus7 Systems Consulting Java Developer Interview Questions and Answers

Abstraction focuses on hiding implementation details, while encapsulation bundles data and methods into a single unit.

• Abstraction allows us to focus on the essential features of an object while hiding unnecessary details.

• Encapsulation helps in data hiding by restricting access to certain components of an object.

• Abstraction is achieved through abstract classes and interfaces in Java.

• Encapsulation is implemented using ac...read more

Hash table is a data structure that stores key-value pairs and allows for fast retrieval of values based on keys.

• Hash table uses a hash function to map keys to indexes in an array.

• It provides constant time complexity O(1) for insertion, deletion, and retrieval operations.

• Collisions can occur when two keys hash to the same index, which can be resolved using techniques like chaining or open addressing.

PUT is used to update or replace an existing resource, while POST is used to create a new resource.

• PUT is idempotent, meaning multiple identical requests will have the same effect as a single request.

• POST is not idempotent, meaning multiple identical requests may have different effects.

• PUT is used to update an existing resource at a specific URI.

• POST is used to create a new resource under a specific URI.

• PUT requests ar...read more

Spring Boot applications can be deployed using various methods such as embedded servers, Docker containers, and cloud platforms.

• Deploying as a standalone JAR file using embedded servers like Tomcat or Jetty

• Building a Docker image and running the application in a container

• Deploying to cloud platforms like AWS, Azure, or Google Cloud Platform

• Using CI/CD pipelines for automated deployment

Garbage collection in Java is the process of automatically reclaiming memory that is no longer in use by the program.

• Garbage collection is performed by the JVM to free up memory occupied by objects that are no longer referenced by the program.

• It helps in preventing memory leaks and ensures efficient memory management.

• Java provides automatic garbage collection, so developers do not have to manually free up memory.

• Exampl...read more

Various design patterns like Singleton, Factory, Observer, etc. are used to solve common problems in software development.

• Singleton pattern ensures a class has only one instance and provides a global point of access to it.

• Factory pattern creates objects without specifying the exact class of object that will be created.

• Observer pattern defines a one-to-many dependency between objects so that when one object changes stat...read more

Multithreading in Spring Boot allows for concurrent execution of tasks, improving performance and responsiveness.

• Spring Boot provides support for multithreading through the use of @Async annotation.

• By annotating a method with @Async, it will be executed in a separate thread.

• ThreadPoolTaskExecutor can be configured to control the number of threads used for executing async methods.

• Example: @Async public void asyncMethod(...read more

Executor Service is a framework provided by Java to manage and control the execution of tasks in a multithreaded environment.

• It provides a way to manage threads and execute tasks asynchronously.

• It allows for the reuse of threads instead of creating new ones for each task.

• It can handle task scheduling, thread pooling, and thread lifecycle management.

• Example: Executors.newFixedThreadPool(5) creates a thread pool with 5 t...read more