code: public static String hexDump(byte[] array, int offset, int length) {
              if (length < 0) {
                throw new IllegalArgumentException("length: " + length);
              }
              if (length == 0) {
                  return EMPTY_STRING;
              }
              int endIndex = offset + length;
              char[] buf = new char[length << 1];
  
              int srcIdx = offset;
              int dstIdx = 0;
              for (; srcIdx < endIndex; srcIdx ++, dstIdx += 2) {
                  System.arraycopy(
                      HEXDUMP_TABLE, (array[srcIdx] & 0xFF) << 1,
                      buf, dstIdx, 2);
              }
              return new String(buf);
          }
docs: 格式化为16进制字符串
  @param array
  @param offset
  @param length
  @return