Map获取key值

public static void test4(){
    Map<String, Object> map = new HashMap<>();
    map.put("key1",1);
    map.put("key2",2);
    //第一种keySet()
    System.out.println("map.keySet():"+map.keySet());
    Set<String> strings = map.keySet();
    Iterator<String> iterator = map.keySet().iterator();
    while (iterator.hasNext()){
        System.out.println("iterator:"+iterator.next());
    }
    //第二种
    System.out.println("map.entrySet():"+map.entrySet());
    Iterator<Map.Entry<String, Object>> iterator1 = map.entrySet().iterator();
    while (iterator1.hasNext()){
        System.out.println("iterator1:"+iterator1.next());
    }
    //----------
    for (Map.Entry<String, Object> entry : map.entrySet()){
        System.out.println("key:"+entry.getKey()+";value:"+entry.getValue());
    }
}