遍历map的几种方法

遍历map有几种方法，记录一下。

public class MapCollection {
    public static void main(String[] args) {
        HashMap<Integer, String> map = new HashMap<>();
        map.put(1,"小花");
        map.put(2,"小草");
        map.put(3,"小红");
        map.put(4,"小白");

        System.out.println("-----通过Map.keySet()获取key,根据key调用map.get()获取值value------");
        for (Integer key:map.keySet()) {
            System.out.println(key+":"+map.get(key));
        }

        System.out.println("-----通过Map.entrySet()获取迭代器对象iterator,遍历key和value-----");
        Iterator<Map.Entry<Integer, String>> it = map.entrySet().iterator();
        while(it.hasNext()){
            Map.Entry<Integer, String> entry = it.next();
            System.out.println(entry.getKey()+":"+entry.getValue());
        }

        System.out.println("-----通过Map.entrySet()遍历key和value-------");
        for (Map.Entry<Integer,String> entry:map.entrySet()) {
            System.out.println(entry.getKey()+":"+entry.getValue());
        }

        System.out.println("-----通过Map.values()遍历所有的value-----");
        System.out.println("-----此方法无法获key----------");
        for (String value: map.values()) {
            System.out.println(value);
        }
    }
}