如何遍历嵌套的TreeMaps？

Question

我有一组3个嵌套的TreeMaps：

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>();

它存储预订的信息。我试图使用嵌套的while循环遍历它们，以显示已创建的所有预订，但我需要在嵌套的while中使用一种方法来仅显示与相关父对象相关的值。

这就是我所拥有的：

        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";
            }
        }

正如预期的(但不是想要的) ...but，它只是遍历每个TreeMap中的所有条目，直到最后。

有人能帮上忙吗？

Answer 1

它不是很清楚(什么是listOfDays，listOfCourts和listOfTimes?)，但我猜你需要这样的东西：

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";
        }
    }
}

简而言之，一个map可以看作是一组map条目，您可以遍历这个条目集。每个条目都有一个键和一个值。由于在您的示例中，该值是另一个映射，因此您可以对该值重复此操作。