public ArrayList<Integer> findLongestTrainTrack(){
		ArrayList<Integer> maxId = new ArrayList<Integer>();   //最長火車的id序列
		
		for(int i=0 ; i<receivingTrack.length ; i++){
			int count = maxId.size();
			for(int j=maxId.size()-1 ; j>=0 ; j--){
				if(receivingTrack[i].ifEmpty == false){
					
					if(receivingTrack[i].train.size() > receivingTrack[maxId.get(j)].train.size()){
						count = j;
					}
				}
			}
			if(receivingTrack[i].ifEmpty == false)
				maxId.add(count, i);
		}
	
		if(maxId.isEmpty()){   //如果為空
			maxId.add(-1);
		}
		else{
			for(int i: maxId)
			System.out.println("%%" + receivingTrack[i].train.size());
		}
		return maxId;
	}