HashMap的遍历

public class MapTraverse {
        public static void main(String[] args) {
        Map<Integer, String> map = new HashMap<>();
        map.put(1, "小米");
        map.put(2, "华为");
        map.put(3, "Oppo");
        map.put(4, "iphone");
        System.out.println(map.toString());
        //第一种：map.keySet()
        Set<Integer> set = map.keySet();
        for (Integer item : set) {
            String s = map.get(item);
            System.out.println(s);
        }
        System.out.println("---------------------");
        //第二种 map.values()
        for (String s : map.values()) {
            System.out.println(s);
        }
        System.out.println("---------------------");
        //第三种：map.entrySet().iterator();
        Iterator<Map.Entry<Integer, String>> iterator = map.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<Integer, String> next = iterator.next();
            System.out.println(next.getKey() + ":" + next.getValue());
        }
        //第四种： map.entrySet()
        Set<Map.Entry<Integer, String>> entries = map.entrySet();
        for (Map.Entry<Integer, String> entry : entries) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }
    }
}