Introduction to Java

Chapter 1: Introduction to Java

1.1 What is Java?

Java is a high-level, object-oriented, platform-independent programming language developed by Sun Microsystems (now owned by Oracle). It is used to build web, mobile, desktop, and enterprise applications.

It follows the WORA principle — Write Once, Run Anywhere — allowing compiled code to run on any device with the JVM (Java Virtual Machine).

1.2 History of Java

Java was created by James Gosling and his team at Sun Microsystems in 1995. Originally named Oak, it was designed for interactive television, but later rebranded as Java and optimized for web applications.

1.3 Features of Java

Simple: Easy to learn and use, especially for those familiar with C/C++.
Object-Oriented: Promotes modularity, code reuse, and better structure.
Platform-Independent: Runs on any OS with JVM.
Secure: Uses sandboxing and classloaders to prevent malicious code.
Robust: Strong memory management, garbage collection, and exception handling.
Multithreaded: Supports multitasking by running multiple threads simultaneously.
Distributed: Enables building network-based applications using RMI and EJB.

1.4 Java Editions

Java SE (Standard Edition): Core Java features for desktop and server-side apps.
Java EE (Enterprise Edition): Advanced tools for large-scale enterprise applications.
Java ME (Micro Edition): Used in mobile devices and embedded systems.

1.5 Java Architecture

Compilation Process:

Java Source Code (.java) — Written by the programmer
Java Compiler — Converts code to Bytecode (.class)
JVM — Executes Bytecode across platforms

Flow: Source Code → Compiler → Bytecode → JVM → Output

1.6 Java Applications in Real Life

Android Mobile Apps
Web Portals (IRCTC, Flipkart backend)
Banking & Financial Applications
Embedded Systems
Scientific Research Tools
Gaming (e.g., Minecraft)

1.7 Advantages of Java

Free and Open Source
Portable and Scalable
Large Community Support
Rich APIs and Libraries
Powerful IDEs (Eclipse, IntelliJ IDEA)

📚 Chapter Summary

This chapter introduced the core concepts of Java — its definition, history, architecture, features, editions, and real-world use cases.

❓ FAQs (Frequently Asked Questions)

Q1: What is Java used for?
A: Java is used in mobile apps, web applications, banking systems, scientific tools, games, and embedded systems.

Q2: What does WORA mean in Java?
A: WORA stands for "Write Once, Run Anywhere" — Java programs run on any device with JVM.

Q3: What are the key features of Java?
A: Java is object-oriented, platform-independent, secure, robust, simple, multithreaded, and distributed.

Q4: What is the role of JVM in Java?
A: The Java Virtual Machine (JVM) runs the compiled bytecode, ensuring cross-platform compatibility.

Q5: What are the main Java editions?
A: Java SE, Java EE, and Java ME.

Q6: Is Java still relevant in 2025?
A: Absolutely. Java powers Android apps, enterprise systems, and high-performance software globally.

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