code: public MessageBuilder replace(String target, String replacement)
      {
          int index = builder.indexOf(target);
          while (index != -1)
          {
              builder.replace(index, index + target.length(), replacement);
              index = builder.indexOf(target, index + replacement.length());
          }
          return this;
      }
docs: Replaces each substring that matches the target string with the specified replacement string.
  The replacement proceeds from the beginning of the string to the end, for example, replacing
  "aa" with "b" in the message "aaa" will result in "ba" rather than "ab".
  
  @param  target
  the sequence of char values to be replaced
  @param  replacement
  the replacement sequence of char values
  
  @return The MessageBuilder instance. Useful for chaining.