Java: System.getenv("APPDATA") returns null, now what?

I开发者_开发知识库 just found out that when a Java program is launched on Windows via "Run As..." (from the executable's context menu) as a different user, a call to System.getenv("APPDATA") will return null, rather than the usual application data folder.

Now, I'm kind of a noob when it comes to Windows folders and such, so my question is, how should I deal with this situation when my program has to be able to store its data somewhere in order to work correctly? More specifically, if System.getenv("APPDATA") returns null, am I even allowed to store any data at all, and if so, where? Thanks in advance!

Okay, I solved my own problem using JNA:

com.sun.jna.platform.win32.Shell32Util.getFolderPath(int nFolder)

where nFolder = 0x001a for the application data folder and nFolder = 0x001c for the local application data folder. On Windows XP, the output is

C:\Documents and Settings\[UserName]\Application Data

C:\Documents and Settings\[UserName]\Local Settings\Application Data

Most importantly, this does not return null when the program is launched via Run As.

Yes you are always allowed to store data. You can use temp directory to store you data. You can get temp directory by System.getProperty("java.io.tmpdir");.

Also if you set an environment variable in windows, I noticed that java doesn't pick it up until I restarted the OS.