code: public FulltextMatch addPattern(
                      final String pattern
                      )
      {
          if (pattern == null  ||  pattern.length() == 0) {
              throw new IllegalArgumentException( "no pattern specified" );
          }
  
          _patterns.add( pattern );
  
          return this;
      }
docs: Appends the specified matching pattern.
  
  @param   pattern
  the matching pattern to be appended.
  @throws  IllegalArgumentPointerException
  if the specified pattern is null.