How exactly does java compilation take place?

Question

Confused by java compilation process

OK i know this: We write java source code, the compiler which is platform independent translates it into bytecode, then the jvm

Answer 1

Short Explanation

Write code on a text editor, save it in a format that compiler understands - ".java" file extension, javac (java compiler) converts this to ".class" format file (byte code - class file). JVM executes the .class file on the operating system that it sits on.

Long Explanation

Always remember java is not the base language that operating system recognizes. Java source code is interpreted to the operating system by a translator called Java Virtual Machine (JVM). JVM cant understand the code that you write in a editor, it needs compiled code. This is where a compiler comes into picture.

Every computer process indulges in memory manipulation. We cant just write code in a text editor and compile it. We need to put it in the computer's memory, i.e save it before compiling.

How will the javac (java compiler) recognize the saved text as the one to be compiled? - We have a separate text format that the compiler recognizes, i.e .java. Save the file in .java extension and the compiler will recognize it and compile it when asked.

What happens while compiling? - Compiler is a second translator(not a technical term) involved in the process, it translates user understood language(java) into JVM understood language(Byte code - .class format).

What happens after compiling? - The compiler produces .class file that JVM understands. The program is then executed, i.e the .class file is executed by JVM on the operating system.

Facts you should know

1) Java is not multi-platform it is platform independent.

2) JVM is developed using C/C++. One of the reason why people call Java a slower language than C/C++

3) Java byte code (.class) is in "Assembly Language", the only language understood by JVM. Any code that produces .class file on compilation or generated Byte code can be run on the JVM.