Java中怎样遍历Map的所有的元素

JDK1.4中

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    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();

    }

    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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    private Hashtable emails = new Hashtable();

    private Hashtable emails = new Hashtable();  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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     //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 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));

       }
   

     //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 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));

       }

 

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【责编:landy】

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