如何迭代TreeMap？ [重复]

4 回答

• 5

  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）

  回复于 2024-04-26T04:21:48+08:00
• 199

  //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);
     }
  

  回复于 2024-04-26T04:21:48+08:00
• 1

  只是指出迭代任何 Map 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());
      }
      }
  

  回复于 2024-04-26T04:21:48+08:00
• 25

  使用Google Collections，假设K是您的密钥类型：

  Maps.filterKeys(treeMap, new Predicate<K>() {
    @Override
    public boolean apply(K key) {
      return false; //return true here if you need the entry to be in your new map
    }});
  

  如果您还需要该值，也可以使用 filterEntries .

  回复于 2024-04-26T04:21:48+08:00