Java TreeMap 小例子

// wordcount

public static void mapTest() {      String text = "Constructs a list containing the elements of the specified"           + "collection, in the order they are returned by the collection's iterator."          + "c the collection whose elements are to be placed into this list"          + " NullPointerException if the specified collection is null ";            TreeMap<String, Integer> map = new TreeMap<String, Integer>();      String[] words = text.split("[ \n\t\r.,;:!?(){]");            for (int i = 0; i < words.length; i++) {        String key = words[i].toLowerCase();        if (key.length() > 0) {          if (map.get(key) == null)            map.put(key, 1);          else {            int value = map.get(key).intValue();            value++;            map.put(key, value);          }        }      }      Set<Map.Entry<String, Integer>> entrySet = map.entrySet();      for (Map.Entry<String, Integer> entry: entrySet)        System.out.println(entry.getValue() + "\t" + entry.getKey());}