public static String toString(final byte[] b, int off) {
    if (b == null) {
      return null;
    }
    int len = b.length - off;
    if (len <= 0) {
      return "";
    }
    try {
      return new String(b, off, len, UTF8_CSN);
    } catch (UnsupportedEncodingException e) {
      // should never happen!
      throw new IllegalArgumentException("UTF8 encoding is not supported", e);
    }
  }
This method will convert utf8 encoded bytes into a string. If the given byte array is null,
this method will return null.
@param b   Presumed UTF-8 encoded byte array.
@param off offset into array
@return String made from <code>b</code> or null
hbase-common/src/main/java/org/apache/hadoop/hbase/util/Bytes.java