map 比较(两个map的key，value 是否一样)

1. 用equals 比较

    public static void main(String[] args) {
        List> list = new ArrayList<>();
        Map map1= new HashMap<>();
        map1.put("name","郭");
        map1.put("objId","1");

        list.add(map1);


        Map map2= new HashMap<>();
        map2.put("name","郭2");
        map2.put("objId","2");

        list.add(map2);
        //
        Map map3= new HashMap<>();
        map3.put("name","郭2");
        map3.put("objId","2");


        Map map4= new HashMap<>();
        map4.put("name","郭3");
        map4.put("objId","2");

        // true
        if(list.contains(map3)){
            System.out.println("hhh");
        }

        // false
        if(list.contains(map4)){
            System.out.println("hhh");
        }

        // true(可以用来比较两个map 的key ，value 是否一样)
        System.out.println(map2.equals(map3));
       
    }

底层逻辑：

 

 public boolean equals(Object o) {
        if (o == this)
            return true;

        if (!(o instanceof Map))
            return false;
        Map m = (Map) o;
        if (m.size() != size())
            return false;

        try {
            for (Entry e : entrySet()) {
                K key = e.getKey();
                V value = e.getValue();
                if (value == null) {
                    if (!(m.get(key) == null && m.containsKey(key)))
                        return false;
                } else {
                    if (!value.equals(m.get(key)))
                        return false;
                }
            }
        } catch (ClassCastException unused) {
            return false;
        } catch (NullPointerException unused) {
            return false;
        }

        return true;
    }