Top 250 Java Interview Questions and Answers

Classloaders are responsible for loading classes into the JVM at runtime.

• Java has three built-in classloaders: bootstrap, extension, and system.

• Custom classloaders can be created to load classes from non-standard sources.

• Classloaders follow a delegat...read more

Stream and collection api usage involves manipulating data using streams and collections in Java.

• Stream API provides a way to process collections of objects in a functional way.

• Collection API provides data structures to store and manipulate groups of...read more

Java 8 introduced the concept of functional programming with the addition of lambda expressions and streams.

• Lambda expressions allow for concise code and easier parallel programming.

• Streams provide a way to work with collections of objects in a funct...read more

Java 8 introduced several improvements including lambda expressions, functional interfaces, streams, and default methods.

• Lambda expressions allow for more concise code and easier parallel programming.

• Functional interfaces enable the use of lambda exp...read more

No, controller and service annotations serve different purposes in a software application.

• Controller annotations are used to define the entry points for incoming requests and map them to specific methods in a controller class.

• Service annotations are ...read more

Yes, I have knowledge of both Java and Python.

• I have experience in developing robotics applications using Java and Python.

• I am familiar with object-oriented programming concepts in both languages.

• I have worked on projects involving robotics simulatio...read more

The Executor framework in Java provides a high-level API for managing and controlling thread execution.

• Executor: The simplest interface for executing tasks asynchronously.

• ExecutorService: Extends Executor, provides methods for managing termination an...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 execu...read more

C++ and Java are programming languages used for software development.

• C++ is a high-performance language used for system programming, game development, and other performance-critical applications.

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

Java 8 introduced features like lambda expressions, functional interfaces, streams, and default methods.

• Lambda expressions allow you to pass functionality as an argument to a method.

• Functional interfaces have a single abstract method and can be used ...read more

The @Controller annotation is used to create a controller class in Spring MVC, while @RestController is used to create RESTful web services.

• The @Controller annotation is used to create a controller class in Spring MVC, which is used to handle traditi...read more

Functional interfaces are interfaces with a single abstract method, used in Java to enable lambda expressions.

• Functional interfaces allow lambda expressions to be used as instances of the interface.

• They provide a way to implement functional programmi...read more

Using Java Stream API to find characters in a string efficiently and concisely.

• Streams can be created from a string using `chars()` method: `String str = "hello"; str.chars()`.

• To filter specific characters, use `filter()`: `str.chars().filter(c -> c ...read more

Commonly used functional interfaces include Predicate, Consumer, Supplier, and Function.

• Predicate: used for boolean-valued functions of one argument.

• Consumer: used for operations that take in one argument and return no result.

• Supplier: used for opera...read more

Frameworks in Java provide pre-written code to help developers build applications more efficiently.

• Frameworks like Spring, Hibernate, and Struts provide structure and functionality to Java applications.

• Frameworks help developers follow best practices...read more

Spring annotations are used to provide metadata to Spring framework classes and components.

• Annotations are used to configure Spring beans, dependency injection, AOP, and more

• Examples include @Component, @Autowired, @RequestMapping, @Service, @Reposit...read more

Spring Boot is a framework that simplifies the development of Java applications by providing pre-configured settings and tools.

• Spring Boot eliminates the need for manual configuration by providing defaults for most settings.

• It includes embedded serve...read more

Requestparam vs pathvariable and syntax

• RequestParam is used to extract query parameters from the URL, while PathVariable is used to extract values from the URI template

• RequestParam syntax: @RequestParam("paramName") String paramValue

• PathVariable synt...read more

The database used by Java front end developers varies depending on the project requirements.

• Common databases used by Java front end developers include MySQL, PostgreSQL, Oracle, and MongoDB.

• The choice of database depends on factors such as scalabilit...read more

Values can be sent without using sendkeys method by directly manipulating the DOM or using JavaScriptExecutor.

• Use JavaScriptExecutor to execute JavaScript code to set values of input fields.

• Find the element using appropriate locators and then use Jav...read more

Spring beans are objects managed by the Spring IoC container, providing configuration and lifecycle management.

• Spring beans are instantiated, configured, and managed by the Spring IoC container.

• They can be defined in XML, Java annotations, or Java co...read more

Bean factory is a container for managing beans in Spring framework.

• Bean factory is responsible for creating, managing, and configuring beans in a Spring application.

• It uses inversion of control (IoC) to manage the beans.

• Beans are defined in a configu...read more

The get method is a function used to retrieve the value of a specified property from an object.

• Used in JavaScript to access the value of a property in an object

• Syntax: objectName.propertyName

• Example: var person = {name: 'John', age: 30}; console.log(...read more

Some important Spring Boot annotations include @SpringBootApplication, @RestController, @Autowired, @RequestMapping, @ComponentScan.

• @SpringBootApplication - Used to mark the main class of a Spring Boot application.

• @RestController - Used to define RES...read more

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

• Lambda expressions: Allow you to pass functionality as an argument to a method.

• Streams: Provide a way to work with sequences of elements.

• Fun...read more

Difference between @Mock and @InjectMock annotations in Java testing

• Use @Mock to create a mock object of a class or interface

• Use @InjectMock to inject the mock object into the class being tested

• Example: @Mock UserService userService; @InjectMock User...read more

Static and default methods in functional interfaces provide utility methods and default implementations for interface methods in real-time applications.

• Static methods in functional interfaces can be used for utility methods that are not tied to a spe...read more