170530、java 迭代hashmap常用的三种方法

@SuppressWarnings("rawtypes")
public class HashMapDemo {    //hashMap遍历
    public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();
        map.put("k1", "v1");
        map.put("k2", "v2");
        map.put("k3", "v3");
        //方法一
        Iterator it = map.entrySet().iterator();
        while(it.hasNext()){
            Map.Entry m = (Map.Entry)it.next();
            System.out.println("key=" + m.getKey() + "," + "value=" + m.getValue());
        }
        System.out.println();
        //方法二
        for(Map.Entry<String, String> m : map.entrySet()){
            System.out.println("key=" + m.getKey() + "," + "value=" + m.getValue());
        }
        System.out.println();
        //方法三
        Iterator iterator = map.keySet().iterator();
        while(iterator.hasNext()){
            String key = (String)iterator.next();
            System.out.println("key=" + key + "," + "value=" + map.get(key));
        }
    }
}