code: public static String encodeToString(byte[] source, int off, int len, int options) {
          byte[] encoded = encode(source, off, len, options);
          return new String(encoded, UTF_8);
      }
docs: 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
  @param options Specified options
  @return The Base64-encoded data as a String
  @see Base64#NO_WRAP
  @throws NullPointerException if source array is null
  @throws IllegalArgumentException if source array, offset, or length are invalid
  @since 2.0