StringBuffer buff = new StringBuffer();  buff.append( prefix + "Stress collection (event=" + getEventName() + "):\n" );  Iterator iter = _stress_set.iterator(); while( iter.hasNext() ) { StressInstance stress = (StressInstance) iter.next();  buff.append( stress.toString( prefix + "\t" ) + "\n" );  }  return buff.toString();
    String toString( String prefix )    {        StringBuffer buff = new StringBuffer();        buff.append( prefix + "Stress collection (event="                     + getEventName() + "):\n" );        Iterator iter = _stress_set.iterator();        while( iter.hasNext() )        {            StressInstance stress = (StressInstance) iter.next();                        buff.append( stress.toString( prefix + "\t" ) + "\n" );        } // while iter        return buff.toString();            } // method toString