Getting a list of environment variables

You can’t anymore. There used to be a method called getenv(String) in java.lang.System but it’s been deprecated since
1.1.8. The only thing you can do now is to use the -D properties flag on the command line when you start your program.

java -Dproperty=value myapp.class

Where property is the name of the property and value is the value you want to as sign it.

You can then retrieve the value of the property using:

getProperty("property");

If you still want to allow the user to set environment variables you can always use them as the value for the property in the startup batch file or shell script like this:

Windows:

   SET ENVVVAR=value
   java -Dproperty=%ENV_VAR% myapp.class

Unix:

   ENV_VAR=value
   export ENV_VAR
   java -Dproperty=$ENV_VAR myapp.class