Core Java Interview Question and Answers
Java is a high-level, object-oriented programming language released in 1995 and has since become one of the most popular programming languages in the world. Java is designed to be platform-independent, meaning that a Java program can run on any platform that has a Java Virtual Machine (JVM) installed. Java is used for developing a wide range of applications, including desktop applications, web applications, mobile applications, and games.
Q: What is Java?
A: Java is a high-level, object-oriented programming language that is widely used for developing desktop, web, and mobile applications.
Q: What are the features of Java?
A: Some of the key features of Java are:
- Object-oriented programming
- Platform independence
- Robustness and reliability
- Multi-threading and concurrency
- Security
- Memory management
- Garbage collection
Q: What is the difference between JDK, JRE, and JVM?
A: JDK (Java Development Kit) is a software development kit that includes the tools needed to develop Java applications, such as the compiler and debugger. JRE (Java Runtime Environment) is a software package that provides the Java virtual machine (JVM) and libraries necessary to run Java applications. JVM (Java Virtual Machine) is the runtime environment in which Java bytecode is executed.
Q: What is a class in Java?
A: A class in Java is a blueprint for creating objects. It defines the properties and methods that the objects will have.
Q: What is an object in Java?
A: An object in Java is an instance of a class. It has its own set of properties and methods.
Q: What is inheritance in Java?
A: Inheritance in Java is the mechanism by which a subclass inherits properties and methods from its superclass.
Q: What is polymorphism in Java?
A: Polymorphism in Java is the ability of an object to take on many forms. It can be achieved through method overriding and method overloading.
Q: What is encapsulation in Java?
A:Encapsulation in Java is the mechanism of hiding the implementation details of a class and exposing only the necessary methods and properties.
Q: What is an interface in Java?
A: An interface in Java is a collection of abstract methods that can be implemented by any class that implements the interface.
Q: What is a package in Java?
A: A package in Java is a collection of related classes and interfaces that can be used in a Java application.
Q: What is a constructor in Java?
A: A constructor in Java is a special method that is used to initialize an object of a class.
Q: What is a static method in Java?
A: A static method in Java is a method that belongs to the class rather than an instance of the class. It can be called using the class name, without the need to create an object of the class.
Q: What is the difference between an abstract class and an interface?
A: An abstract class in Java can have both abstract and non-abstract methods, and it can be used as a base class for other classes. An interface in Java can only have abstract methods, and it defines a set of methods that a class must implement. A class can implement multiple interfaces, but it can only inherit from one class.
Q: What is a thread in Java?
A: A thread in Java is a lightweight process that can execute concurrently with other threads. It is used to achieve multitasking and concurrency in Java applications.
Q: What is synchronization in Java?
A: Synchronization in Java is the mechanism of controlling access to shared resources by multiple threads. It is used to prevent race conditions and other concurrency issues.
Q: What is an exception in Java?
A: An exception in Java is an event that occurs during the execution of a program and disrupts the normal flow of the program. It can be caught and handled using try-catch blocks.
Q: What is a try-catch block in Java?
A: A try-catch block in Java is used to catch and handle exceptions that occur during the execution of a program. The code that may throw an exception is placed inside the try block, and the code that handles the exception is placed inside.
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