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Let's dive

alpha : testing in own organization
beta : testing in public
nightly build : daily build or nightly build is the practice of completing software build of the latest version of program on a daily basis.

JEE - Java Enterprise Edition (for enterprise level applications)
JSE - Java Standard Edition (for stand alone)
JME - Java Micro Edition (for mobiles)

History of Java

History of Java

Benefits of Java and its features

  1. Simple and easy to learn.
  2. Java is almost fully OOP.
  3. Java is robust and secure.
  4. Architecture neutral and portable.
  5. Multithreading
  6. Provides High Performance

How is Java platform independent?

The meaning of platform independent is that, the java source code can run on all operating systems.
A program is written in a language which is a human readable language. It may contain words, phrases etc which the machine does not understand. For the source code to be understood by the machine, it needs to be in a language understood by machines, typically a machine-level language.
So, here comes the role of a compiler. The compiler converts the high-level language (human language) into a format understood by the machines. Therefore, a compiler is a program that translates the source code for another program from a programming language into executable code.
This executable code may be a sequence of machine instructions that can be executed by the CPU directly, or it may be an intermediate representation that is interpreted by a virtual machine. This intermediate representation in Java is the Java Byte Code.

Step by step Execution of Java Program

  1. Whenever, a program is written in JAVA, the javac compiles it. The result of the JAVA compiler is the .class file or the bytecode and not the machine native code (unlike C compiler).
  2. The bytecode generated is a non-executable code and needs an interpreter to execute on a machine. This interpreter is the JVM and thus the Bytecode is executed by the JVM.
  3. And finally program runs to give the desired output.

Execution with figure

Write once, run everytime.