JAVA /
JAVA ENVIRONMENT

The Java building-executing structure:

Java source code -> Java Compiler -> Bytecode -> Java Virtual Machine -> Machine code

The source code is made by developers. The source code is stored in .java text files.

The Java Compiler creates bytecode from the source code. This code is platform-independent. Usually, the bytecode is stored in .class files or in a single .jar file.

The Java Virtual Machine (JVM) itself is platform-dependent and installed on a platform like Linux, System (Apple) or Windows.

On application launch, the JVM compiles the bytecode into machine code of the given platform and executes it.

Java Runtime Environment (JRE):

• Contains the JVM and libraries.

• A library means a pre-made collection of .class files (byte codes), organized into folders.

Java Development Kit (JDK):

• Contains the JRE and compilers and JavaDocs and Java debuggers.

• The JDK is for software developers.

• There can be several compilers for different purposes and/or from different JDK creators.

• JavaDocs is an automated documentation routine.

• Debuggers are for checking the source code for purpose, stability and exceptions.

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