How to get environment variables in Java ?

Environment variables are stored in a small area of memory available to all running programs.

Environment variables in Windows

Set environment variables

Temporary and disappear on closing the command window

set var=C:\temp

Permanent setting

Right-click on My Computer and choose "Properties"

Click "Advanced" tab, Click the button "Environment Variables"

• User variables : applies only to the current user
• System variable : applies to the whole system

To display value of variable

echo %var%

Environment variables in Linux

To see a list of the environment variables that are already set

$ env

To set environment variable

$ var=$HOME/projects/src/test

To display value of variable

$ echo $var

Use export when creating variables to ensure they will be global in scope

$ export var=$HOME/projects/src/test

Get value of environment variables

For one variable

String variable = System.getenv("var");

For all variables

Map variables = System.getenv();

for (Map.Entry entry : variables.entrySet()) {

  String name = entry.getKey();     

  String value = entry.getValue();     

  System.out.println(name + "=" + value);  

}