Java Interview Questions for Experienced

What are the principles of Object-Oriented Programming (OOP) and how are they applied in Java?
Answer: Principles include encapsulation, inheritance, and polymorphism. In Java, classes and objects are used to implement these principles.
Explain the difference between overloading and overriding in Java.
Answer: Overloading involves having multiple methods with the same name but different parameters in the same class. Overriding occurs when a subclass provides a specific implementation for a method that is already defined in its superclass.
How does Java handle multithreading, and what is the significance of the synchronized keyword?
Answer: Java supports multithreading using the Thread class or implementing the Runnable interface. The synchronized keyword is used to control access to critical sections, preventing multiple threads from accessing them simultaneously.
What is the purpose of the volatile keyword in Java?
Answer: The volatile keyword is used to indicate that a variable's value may be changed by multiple threads simultaneously. It ensures that the variable is always read from and written to the main memory.

Explain the concept of garbage collection in Java.
Answer: Garbage collection is the process of automatically identifying and reclaiming memory occupied by objects that are no longer in use. The Java Virtual Machine (JVM) manages garbage collection.
What are annotations in Java, and how are they used?
Answer: Annotations provide metadata about a program that is not part of the program itself. They are used for providing information to the compiler, such as method deprecation, code generation, etc.
What is the difference between the equals() method and the hashCode() method?
Answer: The equals() method is used to compare the contents of two objects for equality, while the hashCode() method returns an integer hash code value for an object. For correctness, if two objects are equal, their hash codes must be the same.
Explain the Observer design pattern and provide an example of its implementation in Java.
Answer: The Observer pattern defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified. An example in Java is the use of Observable and Observer interfaces.

What is the purpose of the Java Servlet API, and how does it differ from JSP?
Answer: The Java Servlet API provides a way to generate dynamic content on the web. Servlets are Java classes that handle requests and responses. JSP (JavaServer Pages) is a technology that allows embedding Java code in HTML pages to create dynamic content.
Explain the role of JDBC (Java Database Connectivity) in enterprise applications.
Answer: JDBC is used for database connectivity in Java. It provides a standard interface to connect to relational databases, send SQL queries, and process results.

What are the key features of the Spring Framework, and how does it address common challenges in Java development?
Answer: Key features include dependency injection, aspect-oriented programming, and various modules for different concerns. Spring simplifies development, promotes modular and testable code, and addresses many enterprise-level challenges.
Explain the concept of Dependency Injection (DI) in the context of Spring.
Answer: Dependency Injection is a design pattern in which an object receives its dependencies from an external source. In Spring, DI is achieved through the IoC (Inversion of Control) container, which manages object creation and their dependencies.

What is Hibernate, and how does it differ from JDBC in terms of database interaction?
Answer: Hibernate is an object-relational mapping (ORM) framework for Java that provides a higher-level, more object-oriented approach to database interaction. It maps Java objects to database tables and simplifies database access.
Explain the concept of Hibernate caching.
Answer: Hibernate caching is a mechanism used to store frequently accessed data in memory. It improves performance by reducing the number of database queries needed to retrieve data.

What are microservices, and how does Spring Boot support the development of microservices?
Answer: Microservices is an architectural style where an application is composed of loosely coupled, independently deployable services. Spring Boot simplifies the development of microservices by providing an opinionated framework with embedded servers and streamlined configurations.

What are the key features introduced in Java 8, and how have they impacted Java development?
Answer: Key features include lambda expressions, the Stream API, functional interfaces, and the java.time package. These features enhance code conciseness, promote functional programming, and improve date and time handling.

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