Why Isn't XFile a Subclass of File?

This would seem to make sense, particularly where a File object is used as an argument in the constructor for instances of FileInputStream() or RandomAccessFile(). Unfortunately, nearly all the methods in the File class interact directly with the JNI - it is not possible to interpose XFile as a filesystem-independent layer. In addition, classes that take a File in the constructor also work directly with the JNI. Eventually we expect XFile to be subsumed by an Extended Filesystem API in a future release of the Java JDK.