There are certain things that the JVM always knows about, that you might like to know about, too. These things consist of information about the user's working environment. That's why they are called system properties.
Below are listed some of the more commonly referenced system properties. For example, your application might want to perform some specific behavior if the underlying platform is Windows, or you might want to open a JFileChooser dialog that allows the user to save a file, and have it present the user's home directory as its starting location.
|user.dir||User's current working directory|
|user.home||User's home directory|
|user.name||Account name for currently logged in user|
|file.separator||File separator ...|