code: public static String encodeToString(final byte[] source, int off, int len) {
          byte[] encoded = encode(source, off, len);
          return new String(encoded, US_ASCII);
      }
docs: Encodes a byte array into Base64 string.
  
  @param source The data to convert
  @param off The data offset of what to encode.
  @param len The number of bytes to encode.
  @return The Base64-encoded data as a String
  @throws NullPointerException if source array is null
  @since 2.0