遍历Map的几种方法(转载)

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 m = 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