public static long fromHex(String string) {
        return UnsignedLongs.parseUnsignedLong(string, 16);
    }
@Test
    public void fromHex() throws Exception {
        assertEquals(15, Tools.fromHex("0f"));
        assertEquals(16, Tools.fromHex("10"));
        assertEquals(65535, Tools.fromHex("ffff"));
        assertEquals(4096, Tools.fromHex("1000"));
        assertEquals(0xffffffffffffffffL, Tools.fromHex("ffffffffffffffff"));
    }