new ZipLong(0X30304B50L);
private static boolean isZip(File file) throws IOException {
byte[] sig = new byte[4];
if (readFully(file, sig)) {
ZipLong start = new ZipLong(sig);
return ZipLong.LFH_SIG.equals(start) // normal file
|| EOCD_SIG.equals(start) // empty zip
|| ZipLong.DD_SIG.equals(start) // split zip
|| SINGLE_SEGMENT_SPLIT_MARKER.equals(start);
}