Java

JAVA
- Java is a high-level Programming Language
- Used to develop web, desktop, enterprise and mobile application
- Simple, secure, portable and platform independent
- Follows the principle of OOPs

Java Features
- Mobile Applications(Android)
- Web and Desktop Applications
- Scientific Application
- Database connections
- Banking and Finance Systems

History of Java
- Java was developed by James Gosling at Sun Microsystems in 1995
- Originally it was called "Oak"
- Later the name was changed to "Java"
- In 2009, Oracle acquired Sun Microsystems
- Java is the most popular language in the world

JVM (Java Virtual Machine)
- JVM is the heart of java
- Virtual Machine that runs the Java bytecode
- Provides Platform independence
- Performs class loading ,bytecode verification, code execution, memory management, ect

JRE (Java Runtime Environment)
- JRE is the implementation of JVM
- Includes everything required to run a java program
- Contains JVM + core libraries + other supporting files

JDK (Java Development Kit)
- JDK is a complete package
- Used by developers to develop, compile, debug and run java programs
- It contains JRE + development tools

1. JVM - Runs the java code
2. JRE - Runs the java program
3. JDK - Develops + Runs the java program

How Java Program Executes?

Execution flow of a java program
- we writes code as .java file
- compiler (javac) converts it into bytecode(.class file)
- JVM loads .class file and executes the code
- JVM converts bytecode into machine specific code
- Then the output is displayed