getenv : Java Glossary


System.getenv is not considered 100% kosher, but it will get you the environment. It was deprecated in some JDK (Java Development Kit) s, then later resurrected. On windows is it key names are case-insenstive, on other platforms they are case-sensitive. The is no corresponding System. setenv, but you can set up the environment for an execed process. getenv was deprecated for a while then reinstated.
The method is System.getenv( key ) not System.get Env( key ). The name violates the usual conventions.
Where System.getenv has been deprecated. What do you do instead?
  1. Use a properties file

    This has the advantage of being platform independent.
  2. Use the <APPLET <PARAM tags

    which generate a Property. This only works for Applets.
  3. Pass the parameters in on the command line

    There are several ways of doing this. These techniques only work in applications, not Applets.
    • Named parm technique

      the string flavour=strawberry will appear as arg[0] in your main method.
      java.exe MyClass flavour=strawberry
    • Simple parm replacement technique

      the string strawberry will appear as arg[0] in your main method. The % works in Windows, NT, 4DOS and tcc. You may need to do something slightly different in other OSes (Operating Systems).
      set flavour=strawberry
      java.exe MyClass %flavour%
    • -D technique

      System property flavour with value "strawberry "" will be accessible via System.getProperty(flavour"); Make sure you put the -D before your classname or else you will find -Dflavour=strawberry appearing at arg[0] instead. Contrary to rumour, this feature is also available in  Java version 1.6 or later. Make sure you use an upper case

      set flavour=strawberry
      java.exe -Dflavour=%flavour% MyClass

Learning More

Oracle’s Javadoc on System.getenv : available:

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