如何迭代嵌套TreeMaps？

Question

我有一組3個嵌套的樹狀圖：

TreeMap<DayOfWeek, TreeMap<Court, TreeMap<Time, String>>> keyDay = new TreeMap<DayOfWeek, TreeMap<Court, TreeMap<Time, String>>>(); 
TreeMap<Court, TreeMap<Time, String>> keyCourt = new TreeMap<Court, TreeMap<Time, String>>(); 
TreeMap<Time, String> keyTime = new TreeMap<Time, String>(); 

其中存儲預訂信息。我試圖通過使用嵌套while循環遍歷它們來顯示所有已創建的預訂，但是我需要一種嵌套whiles的方式來顯示與相關父級相關的值。

這是我有：

 Iterator listOfDays = keyDay.keySet().iterator(); 
    Iterator listOfCourts = keyCourt.keySet().iterator(); 
    Iterator listOfTimes = keyTime.keySet().iterator(); 
    String output; 

    while (listOfDays.hasNext()) { 
     DayOfWeek currentDay = (DayOfWeek) (listOfDays.next()); 
     output += currentDay.toString() + "\n----------\n"; 
     while (listOfCourts.hasNext()){ 
      Court currentCourt = (Court) (listOfCourts.next()); 
      output += currentCourt.toString() + ":\n"; 
      while (listOfTimes.hasNext()){ 
       Time currentTime = (Time) (listOfTimes.next()); 
       String currentName = (String) keyTime.get(currentTime); 
       output += currentTime.toString() + " - " + currentName + "\n"; 
      } 
     } 

...但預期（但不想要的），它只是通過每個TreeMap中直到結束所有條目進行迭代。

任何人都可以幫忙嗎？

Answer 1

這不是很清楚（是什麼listOfDays，listOfCourts和listOfTimes？），但我想你需要的東西是這樣的：

for (Map.Entry<DayOfWeek, TreeMap<Court, TreeMap<Time, String>>> dayEntry : keyDay.entrySet()) { 
    DayOfWeek currentDay = dayEntry.getKey(); 
    output += currentDay.toString() + "\n----------\n"; 
    for (Map.Entry<Court, TreeMap<Time, String>> courtEntry : dayEntry.getValue().entrySet()) { 
     Court currentCourt = courtEntry.getKey(); 
     output += currentCourt.toString() + ":\n"; 
     for (Map.Entry<Time, String> timeEntry : currentCourt.getValue().entrySet()) { 
      Time currentTime = timeEntry.getKey(); 
      String currentName = timeEntry.getValue(); 
      output += currentTime.toString() + " - " + currentName + "\n"; 
     } 
    } 
} 

總之，地圖可以被看作是一組地圖項，你可以遍歷這個入口集。每個條目都有一個鍵和一個值。由於在您的情況下，值是另一個地圖，您可以重複此操作的值。