使用java.util.prefs.Preferences保存/获取首选项会导致BackingStoreException

private static Preferences systemPrefs = Preferences.systemNodeForPackage (SomeClass.class);

String someString = systemPrefs.put(\"someKey\", \"someValue\");

String someString = systemPrefs.get(\"someKey\", \"someDefaultValue\");

java.util.prefs.FileSystemPreferences syncWorld
VARNING: Couldn\'t flush system prefs: java.util.prefs.BackingStoreException: /etc/.java/.systemPrefs/edu create failed.