If I use the Preference API to store user or system preferences, where are they stored on Windows and Unix?
I have to extend n002213fs' answer, because it seems to me, that the Storage Location is a big mess. Note that Windows saves it in the Windows Registry and Unix saves it in prefs.xml-files.
HKEY_CURRENT_USER\Software\JavaSoft\PrefsHKEY_CURRENT_USER\Software\JavaSoft\PrefsHKEY_CURRENT_USER\Software\Wow6432Node\JavaSoft\PrefsSystem.getProperty("java.util.prefs.userRoot") or (if the previous value is not set) ~/.java/.userPrefsHKEY_LOCAL_MACHINE\Software\JavaSoft\PrefsHKEY_LOCAL_MACHINE\Software\JavaSoft\PrefsHKEY_LOCAL_MACHINE\Software\Wow6432Node\JavaSoft\PrefsSystem.getProperty("java.util.prefs.systemRoot") or (if the previous value is not set) System.getProperty("java.home")+"/.systemPrefs" (System.getProperty("java.home") might be /etc/.java/. You can check it in a terminal with $JAVA_HOME.)