如何迭代TreeMap？

Question

可能重复:
如何迭代Map中的每个条目？

我想迭代a TreeMap,并且对于具有特定值的所有键,我希望将它们添加到新的TreeMap.我怎样才能做到这一点？

Answer 1

假设类型TreeMap <String,Integer>:

for(Map.Entry<String,Integer> entry : treeMap.entrySet()) {
  String key = entry.getKey();
  Integer value = entry.getValue();

  System.out.println(key + " => " + value);
}

(键和值类型可以是任何类别的课程)

Answer 2

    //create TreeMap instance
    TreeMap treeMap = new TreeMap();

    //add key value pairs to TreeMap
    treeMap.put("1","One");
    treeMap.put("2","Two");
    treeMap.put("3","Three");

    /*
      get Collection of values contained in TreeMap using
      Collection values()        
    */
    Collection c = treeMap.values();

    //obtain an Iterator for Collection
    Iterator itr = c.iterator();

    //iterate through TreeMap values iterator
    while(itr.hasNext())
      System.out.println(itr.next());

要么:

   for (Map.Entry<K,V> entry : treeMap.entrySet()) {
        V value = entry.getValue();
        K key = entry.getKey();
   }

要么:

   // Use iterator to display the keys and associated values
   System.out.println("Map Values Before: ");
   Set keys = map.keySet();
   for (Iterator i = keys.iterator(); i.hasNext();) {
     Integer key = (Integer) i.next();
     String value = (String) map.get(key);
     System.out.println(key + " = " + value);
   }

Answer 3

只是指出迭代任何地图的通用方法:

 private <K, V> void iterateOverMap(Map<K, V> map) {
    for (Map.Entry<K, V> entry : map.entrySet()) {
        System.out.println("key ->" + entry.getKey() + ", value->" + entry.getValue());
    }
    }