Top 250 Java Interview Questions and Answers

findFirst returns the first element in a stream, while findAny returns any element in a stream.

• findFirst is deterministic and will always return the first element in a stream, while findAny is non-deterministic and can return any element.

• findAny is u...read more

The Observer pattern is used in SpringBoot for implementing event handling and notification mechanisms.

• The Observer pattern is commonly used in SpringBoot for implementing event listeners and publishers.

• It allows objects to subscribe to and receive n...read more

Meta space is a memory space in Java 8 used to store class metadata.

• Meta space replaces the permanent generation (PermGen) space in Java 8.

• It stores class metadata such as class name, access modifiers, and constant pool.

• Meta space is dynamically size...read more

Concurrency in Java refers to the ability of multiple tasks to run simultaneously within a program.

• Concurrency allows for better utilization of resources by executing multiple tasks at the same time.

• Java provides built-in support for concurrency thro...read more

An abstract method is a method that is declared without an implementation in an abstract class or interface.

• Abstract methods do not have a body and must be implemented by subclasses.

• Abstract classes can have both abstract and non-abstract methods.

• Int...read more

Java is a popular programming language known for its platform independence and object-oriented approach. New features include modules, var keyword, and more.

• Java is a high-level, class-based, object-oriented programming language.

• New features in Java ...read more

To set the default value of a date field to the current date time value, use a script to assign the value.

• Create a client script or business rule to set the default value

• Use the GlideDateTime API to get the current date time value

• Assign the current d...read more

super is a keyword used to access methods and properties of a superclass, while super() is used to call the constructor of a superclass.

• super is used to access methods and properties of a superclass in a subclass.

• super() is used to call the construct...read more

The super keyword is used in Java to refer to the immediate parent class object.

• Used to access methods and variables of the parent class

• Helps in achieving method overriding in inheritance

• Can be used to call the constructor of the parent class

• Example:...read more

Wrapper class in Java 8 is used to convert primitive data types into objects.

• Wrapper classes provide a way to use primitive data types as objects.

• They are used for converting primitive data types into objects and vice versa.

• Examples include Integer, ...read more

Spring Actuator is a feature in Spring Boot that allows monitoring and managing the application.

• Spring Actuator provides endpoints to monitor application health, metrics, info, etc.

• It helps in understanding the internal state of the application and i...read more

Spring bean scopes define the lifecycle and visibility of beans in a Spring application context.

• Singleton: One instance per Spring IoC container. Example: @Bean(name = 'myBean') in a configuration class.

• Prototype: A new instance is created each time ...read more

MVC layers in Java web service help separate concerns for better organization and maintainability.

• Model layer: Represents the data and business logic

• View layer: Handles the presentation of data to the user

• Controller layer: Manages user input and upda...read more

Database connection pool in Java helps manage multiple database connections efficiently.

• Use a connection pool library like HikariCP or Apache DBCP.

• Set up the pool with a maximum number of connections, timeout settings, etc.

• Acquire and release connect...read more

Java HashMap is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values.

• HashMap uses an array of buckets to store key-value pairs.

• The key is hashed to find the index of the bucket where the value is stored.

• If mult...read more

Spring Boot starters are dependency descriptors that simplify the dependency management process in Spring Boot applications.

• Spring Boot starters provide a set of pre-configured dependencies that can be easily included in your project.

• They help in red...read more

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

• Lambda expressions allow for more concise code by enabling functional programming.

• Streams provide a way to process collections of objects in a fun...read more

Design principles in Java focus on creating modular, reusable, and maintainable code.

• Single Responsibility Principle - Each class should have only one responsibility.

• Open/Closed Principle - Classes should be open for extension but closed for modifica...read more

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

• Lambda expressions allow for more concise and readable code.

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

I leverage Spring Java for dependency injection, MVC framework, and transaction management in my projects.

• Utilize Spring's dependency injection to manage object dependencies and improve code maintainability

• Leverage Spring MVC framework for building w...read more

Some technologies available in Java include Java EE, Spring Framework, Hibernate, Apache Struts, and JavaFX.

• Java EE (Enterprise Edition) for building enterprise applications

• Spring Framework for dependency injection and aspect-oriented programming

• Hibe...read more

Java applications can be deployed using various methods such as manual deployment, using build tools like Maven or Gradle, or using containerization platforms like Docker.

• Use build tools like Maven or Gradle to package the application into a JAR or W...read more

The return type for get window handles is an array of strings.

• Return type should be an array of strings

• Each string in the array represents a window handle

• Example: ['handle1', 'handle2', 'handle3']

JPA is a specification while Hibernate is an implementation of JPA.

• JPA is a Java specification for managing relational data in applications.

• Hibernate is an ORM framework that implements the JPA specification.

• Hibernate provides additional features bey...read more

Java 8 introduced several new features including 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...read more

AWT Token is a security token used for authentication and authorization in Java applications.

• AWT stands for Abstract Window Toolkit

• AWT Token is used for managing user authentication and authorization in Java applications

• It provides a secure way to co...read more

Spring JPA is a part of the Spring Data project that makes it easier to work with JPA. Hibernate is a popular ORM framework.

• Spring JPA is a higher level abstraction on top of JPA, providing more features and simplifying development.

• Hibernate is a pow...read more