What is Java?
Java is a high-level, object-oriented programming language used to build software like web applications, mobile apps, desktop programs, and enterprise systems.
History of Java
Java was developed by James Gosling and his team at Sun Microsystems in the early 1990s.
Key Milestones:
- 1991 – Project started as Green Project
- 1995 – Official release of Java
- Originally named Oak, later renamed to Java
- Designed for Write Once, Run Anywhere (WORA)
In 2010, Oracle Corporation acquired Sun Microsystems and now maintains Java.
Java Architecture
Java architecture is designed to be platform-independent. This is achieved using the Java Virtual Machine (JVM).
Components of Java Architecture:
1. Java Source Code
- Written by developers in .java files
2. Java Compiler
- Converts source code into bytecode
- Command used: javac
3. Bytecode
- Intermediate code (.class file)
- Platform-independent
4. Java Virtual Machine (JVM)
- Executes bytecode
- Makes Java platform-independent
5. Java Runtime Environment (JRE)
- Contains JVM + libraries
6. Java Development Kit (JDK)
- Full package for development (JRE + tools)
Java Servers & Providers
Java applications often run on servers called Application Servers or Web Servers.
What is a Server?
A server is a computer or system that provides data, resources, or services to other computers (called clients) over a network.
Popular Java Servers:
1. Apache Tomcat
Type: Web Server
Used for running Java Servlets & JSP
Lightweight and widely used
Provided by Apache Software Foundation
2. GlassFish
Type: Application Server
Supports full Java EE features
Provided by Eclipse Foundation
3. JBoss / WildFly
Type: Application Server
Open-source and powerful
Provided by Red Hat
4. WebLogic Server
Type: Enterprise Application Server
Used in large-scale applications
Provided by Oracle Corporation
5. WebSphere
Type: Enterprise Application Server
Used in banking and enterprise systems
Provided by IBM
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