public static String encodeBytes(byte[] source, int off, int len) {
      byte[] encoded = encodeBytesToBytes(source, off, len);
      try {
        return new String(encoded, PREFERRED_ENCODING);
      } catch (UnsupportedEncodingException uue) {
        return new String(encoded);
      }
    }
Encodes a byte array into Base64 notation.

@param source
         The data to convert
@param off
         Offset in array where conversion should begin
@param len
         Length of data to convert
@return The Base64-encoded data as a String
@throws NullPointerException
          if source array is null
@throws IllegalArgumentException
          if source array, offset, or length are invalid
@since 2.0
lib/src/main/java/com/github/kevinsawicki/http/HttpRequest.java