4

我使用以下复杂的数据结构。

departures = new TreeMap<String,  Map<String,  Set<MyObject>>>();
arrivals=new HashMap<String, Set<MyObject>>();
flights=new HashSet<MyObject>();

然后我使用循环（我也尝试了其他循环）。

for(String dep: nizDep){
    for(String arr: nizArr){
      for(MyObject flight: _flights){
        if(flight.getFrom().equalsIgnoreCase(dep)&&flight.getTo().equalsIgnoreCase(arr)){
                    flights.add(flight);
                 }
                }
                if(!flights.isEmpty()){
            arrivals.put(arr, flights);
                    flights.clear();
                    }
            }
            if(!arrivals.isEmpty()){
            departures.put(dep, arrivals);
            arrivals.clear();
            }
    }
    System.out.println(departures.size()); //result 14
    System.out.println(departures.containsKey("Madrid")); //result true
            arrivals=departures.get("Madrid");
    System.out.println(arrivals.size()); //result 0, arrivals is empty. WHY?

我的问题是如何使用这种复杂的数据结构以及如何从出发中检索到达？

4

2 回答 2

1 
     System.out.println(arrivals.size()); //result 0, arrivals is empty. WHY?

因为当您调用flights.clear();afterarrivals.put(arr, flights);或arrivals.clear();afterdepartures.put(dep, arrivals);时，这会清除您的原始对象（航班和到达）。请带上您的初始化语句，即

        Map<String, Set<MyObject>> arrivals=new HashMap<String, Set<MyObject>>();
        Set<MyObject>(); flights=new HashSet<MyObject>();

在for循环中或替换该语句，如下所示：

                if(!flights.isEmpty()){
                   Set<MyObject> newflights=new HashSet<MyObject>(); 
                    newflights.addAll(flights); //copy elements to new set
                   arrivals.put(arr, newflights);
                    flights.clear();
                }

你也可以用departures.

现在进行检索：

      Set<String> arrivalKeys = departures.keySet();
      Interator<String> arrIter = arrivalKeys.iterator();
      while(arrIter.hasNext()){
        String arrKey = arrIter.next();
        Map<String, Set<MyObject>> arrivals = departures.get(arrKey );
        //use your arrivals map object
      }

同样，您可以flights从arrivals例如检索

对于上述检索到的每个到达：

      Set<String> flightKeys = arrivals.keySet();
      Interator<String> flIter = flightKeys.iterator();
      while(flIter.hasNext()){
        String flKey = flIter.next();
        Set<MyObject> flights = arrivals.get(flKey );
        //use your flights set object
      }
于 2012-10-24T21:21:44.267 回答
0 
arrivals=new HashMap<String, Set<MyObject>>();
departures = new TreeMap<String,  Map<String,  Set<MyObject>>>();
for(String dep: nizDep){
    for(String arr: nizArr){
      for(MyObject flight: _flights){
        if(flight.getFrom().equalsIgnoreCase(dep)&&flight.getTo().equalsIgnoreCase(arr)){
            flights=new HashSet<MyObject>(); 
            flights.add(flight);        
            arrivals.put(arr, flights);     
            departures.put(dep, arrivals);
         }
      }
   }
}
System.out.println(departures.size()); //result 14
if(departures.containsKey("Madrid")) {
    arrivals=departures.get("Madrid");
    System.out.println(arrivals.size());
}

如果您想在到达和航班之间保持一对一的映射，则此代码有效。如果您想保持维护航班集的全局结构，那么您必须创建另一个全局 gflights 对象并将每个航班对象放入其中。

于 2012-10-24T21:46:01.577 回答