code: public static String decode(byte[] in, char[] out, int offset, int utfSize) throws UTFDataFormatException {
          int count = 0, s = 0, a;
          while (count < utfSize) {
              if ((out[s] = (char) in[offset + count++]) < '\u0080') {
                  s++;
              } else if (((a = out[s]) & 0xe0) == 0xc0) {
                  if (count >= utfSize) {
                      throw new UTFDataFormatException("bad second byte at " + count);
                  }
                  int b = in[offset + count++];
                  if ((b & 0xC0) != 0x80) {
                      throw new UTFDataFormatException("bad second byte at " + (count - 1));
                  }
                  out[s++] = (char) (((a & 0x1F) << 6) | (b & 0x3F));
              } else if ((a & 0xf0) == 0xe0) {
                  if (count + 1 >= utfSize) {
                      throw new UTFDataFormatException("bad third byte at " + (count + 1));
                  }
                  int b = in[offset + count++];
                  int c = in[offset + count++];
                  if (((b & 0xC0) != 0x80) || ((c & 0xC0) != 0x80)) {
                      throw new UTFDataFormatException("bad second or third byte at " + (count - 2));
                  }
                  out[s++] = (char) (((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F));
              } else {
                  throw new UTFDataFormatException("bad byte at " + (count - 1));
              }
          }
          return new String(out, 0, s);
      }
docs: Decodes a byte array containing <i>modified UTF-8</i> bytes into a string.
  
  <p>Note that although this method decodes the (supposedly impossible) zero byte to U+0000,
  that's what the RI does too.