Java遍历Map的四种方法

原文地址: http://www.cnblogs.com/kristain/articles/2033566.html

    public static void main(String[] args) {

        Map map = new HashMap();
        map.put("1", "value1");
        map.put("2", "value2");
        map.put("3", "value3");        //第一种：普遍使用，二次取值
        System.out.println("通过Map.keySet遍历key和value：");
        for (String key : map.keySet()) {
            System.out.println("key= "+ key + " and value= " + map.get(key));
        }

        //第二种
        System.out.println("通过Map.entrySet使用Iterator遍历key和value：");
        Iterator<>.Entry> it = map.entrySet().Iterator();
        while (it.hasNext()) {
            Map.Entry entry = it.next();
            System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
        }

        //第三种：推荐，尤其是容量大时
        System.out.println("通过Map.entrySet遍历key和value");
        for (Map.Entry entry : map.entrySet()) {
            System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
        }

        //第四种
        System.out.println("通过Map.values()遍历所有的value，但不能遍历key");
        for (String v : map.values()) {
            System.out.println("value= " + v);
        }
    }

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