Question 1

What is Java?

Accepted Answer

Java is a high-level, class-based, object-oriented programming language designed for general-purpose use. It is platform-independent, secure, and fast, making it a popular choice for developing web, desktop, and mobile applications. Java is highly portable and known for its "write once, run anywhere" capability since it runs on the Java Virtual Machine (JVM).

Question 2

What are the different editions of Java?

Accepted Answer

Java is available in three main editions – Java Standard Edition (Java SE), Java Enterprise Edition (Java EE), and Java Micro Edition (Java ME). Java SE is used for developing desktop applications and general-purpose programming. Java EE includes additional libraries to support the development of scalable, multi-tier, web-based applications. Java ME is specifically designed for small, embedded, and mobile devices with limited resources.

Question 3

What is the difference between JDK, JRE, and JVM?

Accepted Answer

- JDK (Java Development Kit) is a software development environment that includes the tools and libraries needed for developing, compiling, and running Java applications. JDK consists of JRE and development tools.
- JRE (Java Runtime Environment) is a software package that provides the runtime environment required to execute Java applications. It includes JVM, core libraries, and other necessary components.
- JVM (Java Virtual Machine) is an abstract machine that executes Java bytecode. It is a crucial component of the JRE that enables platform independence by converting bytecode into machine language specific to the underlying operating system.

Question 4

What are the basic principles of Object-Oriented Programming (OOP) in Java?

Accepted Answer

Java follows four main principles of Object-Oriented Programming (OOP):
- Encapsulation: Combining data and the methods that operate on that data within a single unit (class), and restricting access to the data from outside the class.
- Inheritance: Allowing one class (subclass) to inherit properties and methods from another class (superclass) to promote reusability and modularity.
- Polymorphism: Permits one interface to be used for multiple data types, allowing a single function or method to handle different types of objects and data.
- Abstraction: Simplifying complex systems by breaking them down into smaller, manageable parts, and focusing only on the essential features and functionality.

Question 5

What is the difference between an interface and an abstract class in Java?

Accepted Answer

- Interface: An interface is a collection of abstract methods without a body (implementation). A class implementing an interface must provide implementations for all its methods. Interfaces can have default and static methods with an implementation but cannot have instance variables or constructors. A class can implement multiple interfaces.
- Abstract Class: An abstract class is a class that cannot be instantiated, but it can have both abstract and non-abstract methods, as well as instance variables and constructors. An abstract class is extended by a subclass, and the subclass is required to provide implementations for abstract methods. A class can only extend one abstract class.

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