public void addOperand(int startTick,int endTick,String text,Lifeline constraintLifeline) throws SequenceDiagramCheckedException {
  if (operands.size() == 0 && this.startTick != startTick) {
    throw new IllegalArgumentException("The start tick of the first operand must be equal to the start tick of the combined fragment");
  }
  operands.add(new Operand(startTick,endTick,text,constraintLifeline));
}

public void addOperand ( int startTick , int endTick , String text , Lifeline constraintLifeline ) throws SequenceDiagramCheckedException { if ( operands . size ( ) == 0 && this . startTick != startTick ) { throw new IllegalArgumentException ( "The start tick of the first operand must be equal to the start tick of the combined fragment" ) ; } operands . add ( new Operand ( startTick , endTick , text , constraintLifeline ) ) ; }
adds an operand with an interaction constraint to the combined fragment .
