getenv : Java Glossary

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getenv
System.getenv is not considered 100% kosher, but it will get you the environment. It was deprecated in some JDKs, 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.getEnv( 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 4NT. You may need to do something slightly different in other OSes. 
      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 JDK 1.1. Make sure you use an upper case D. 
      set flavour=strawberry
java.exe -Dflavour=%flavour% MyClass

Learning More

Sun’s Javadoc on System.getenv : available:
Applet
environment
properties
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