java - What is the cross-platform way of obtaining the path to the local application data directory?

Question

What I need is a platform-independent way of obtaining the path to the local application data directory. System.getenv("LOCALAPPDATA") seems to work only with Windows. How do I go about this?

Answer 1

You could probably say something like (contradict me if I am wrong, or if this a bad approach)

private String workingDirectory;
//here, we assign the name of the OS, according to Java, to a variable...
private String OS = (System.getProperty("os.name")).toUpperCase();
//to determine what the workingDirectory is.
//if it is some version of Windows
if (OS.contains("WIN"))
{
    //it is simply the location of the "AppData" folder
    workingDirectory = System.getenv("AppData");
}
//Otherwise, we assume Linux or Mac
else
{
    //in either case, we would start in the user's home directory
    workingDirectory = System.getProperty("user.home");
    //if we are on a Mac, we are not done, we look for "Application Support"
    workingDirectory += "/Library/Application Support";
}
//we are now free to set the workingDirectory to the subdirectory that is our 
//folder.

Note that, in this code, I am taking full advantage that Java treats '/' the same as '\' when dealing with directories. Windows uses '\' as pathSeparator, but it is happy with '/', too. (At least Windows 7 is.) It is also case-insensitive on it's environment variables; we could have just as easily said workingDirectory = System.getenv("APPDATA"); and it would have worked just as well.