Java中怎样遍历Map的所有的元素

JDK1.4中

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    <FONT color=#0000ff>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();

    }</FONT>

    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

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    Map m = new HashMap();

    for(Object o : map.keySet()){

        map.get(o);

    }

    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。

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    <FONT color=#0000ff>private Hashtable<String, String> emails = new Hashtable<String, String>();</FONT>

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

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     <FONT color=#0000ff>//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));

       }
    </FONT>

     //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));

       }

 

     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

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    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));

       }

    }

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