public static String byte2Hex(int value) {
    if (value > 255 || value < 0) {
      throw new IllegalArgumentException("The int converting to hex should be in range 0~255");
    }
    return String.valueOf(FIRST_CHAR[value]) + String.valueOf(SECOND_CHAR[value]);
  }
Convert an int [0-255] to a hexadecimal string representation.

@param value int value.
fbcore/src/main/java/com/facebook/common/util/Hex.java