按网络字节序从字节数组中拿出8个字节拼装成一个long型

/**
  * 按网络字节序从字节数组中拿出8个字节拼装成一个long型(对应c++中的long long)数据
  *
  * @param from
  * @param fromIndex
  * @return
  */
 public static long getLongLongData(byte[] from, int fromIndex) {

  return (((long) from[fromIndex + 4] & 0xff) << 56)
    + (((long) from[fromIndex + 5] & 0xff) << 48)
    + (((long) from[fromIndex + 6] & 0xff) << 40)
    + (((long) from[fromIndex + 7] & 0xff) << 32)
    + (((long) from[fromIndex] & 0xff) << 24)
    + (((long) from[fromIndex + 1] & 0xff) << 16)
    + (((long) from[fromIndex + 2] & 0xff) << 8)
    + ((long) from[fromIndex + 3] & 0xff);
 }