java如何遍历map的所有的元素（各种方法）

关键字: java如何遍历map的所有的元素（各种方法）
JDK1.4中

Map map = new HashMap(); 
Iterator it = map.entrySet().iterator(); 
while (it.hasNext()) { 
Map.Entry entry = (Map.Entry) it.next(); 
Object key = entry.getKey(); 
Object value = entry.getValue(); 
} 

JDK1.5中,应用新特性For-Each循环

Map map = new HashMap(); 
for(Object o : map.keySet()){ 
    map.get(o); 
} 

返回的 set 中的每个元素都是一个 Map.Entry 类型。

private Hashtable<String, String> emails = new Hashtable<String, String>(); 

   //方法一: 用entrySet() 
   Iterator it = emails.entrySet().iterator(); 
   while(it.hasNext()){ 
    Map.Entry m=(Map.Entry)it.next(); 
    logger.info("email-" + m.getKey() + ":" + m.getValue()); 
   } 
  
   // 方法二：jdk1.5支持，用entrySet()和For-Each循环() 
   for (Map.Entry<String, String> m : emails.entrySet()) { 
   
    logger.info("email-" + m.getKey() + ":" + m.getValue()); 
   } 
  
   // 方法三：用keySet() 
   Iterator it = emails.keySet().iterator(); 
   while (it.hasNext()){ 
    String key; 
    key=(String)it.next(); 
    logger.info("email-" + key + ":" + emails.get(key)); 
   } 

// 方法五：jdk1.5支持，用keySEt()和For-Each循环 

for(Object m: emails.keySet()){ 
    logger.info("email-" + m+ ":" + emails.get(m)); 
   } 

另外 我们可以先把hashMap 转为集合Collection，再迭代输出，不过得到的对象

   Map aa = new HashMap();   
      aa.put("tmp1",new Object()); //追加替换用同样的函数.   
      aa.remove("temp1");//删除   
   for (Iterator i = aa.values().iterator();i.hasNext();){   
           Object temp =i.next();   
   }  //遍历

来个完整的，包含TreeSet的元素内部排序的

public static void main(String[] args) { 
   ArrayList<String> list = new ArrayList<String>(); 
   HashMap<Object,Object> hash = new HashMap<Object,Object>(); 
   TreeMap<Object,Object> treeMap = new TreeMap<Object,Object>(); 
   list.add("a"); 
   list.add("b"); 
   list.add("c"); 
  
   hash.put(3, 3); 
   hash.put(4, 4); 
   hash.put(5, 5); 
   hash.put(6, 6); 
   hash.put(1, 1); 
   hash.put(2, 2); 
  
   treeMap.put(1, 1); 
   treeMap.put(2, 2); 
   treeMap.put(3, 3); 
   treeMap.put(4, 4); 
   treeMap.put(5, 5); 
   treeMap.put(6, 6); 
  
   //list遍历 
   for(String m: list){ 
    System.out.println(m); 
   } 
   // hashmap entrySet() 遍历 
   for(Map.Entry<Object,Object> m: hash.entrySet()){ 
    System.out.println(m.getKey()+"---"+m.getValue()); 
   } 
   //hashmap keySet() 遍历 
   for(Object m: hash.keySet()){ 
    System.out.println(m+"---"+hash.get(m)); 
   } 
   // treemap keySet()遍历 
   for(Object m: treeMap.keySet()){ 
    System.out.println(m+"---"+treeMap.get(m)); 
   } 
}