Java List Set Map判断是否为空

1.List判断是否为空

        List<User> users1 = null;
        //false
        boolean result1 = org.apache.commons.collections.CollectionUtils.isNotEmpty(users1);

        List<User> users2 = new ArrayList<>();
        //false
        boolean result2 = org.apache.commons.collections.CollectionUtils.isNotEmpty(users2);

        List<User> users3 = new ArrayList<>();
        users3.add(new User("yuhan"));
        //true
        boolean result3 = org.apache.commons.collections.CollectionUtils.isNotEmpty(users3);

2.Set判断是否为空

        Set<User> users1 = null;
        //false
        boolean result1 = org.apache.commons.collections.CollectionUtils.isNotEmpty(users1);

        Set<User> users2 = new HashSet<>();
        //false
        boolean result2 = org.apache.commons.collections.CollectionUtils.isNotEmpty(users2);

        Set<User> users3 = new HashSet<>();
        users3.add(new User("yuhan"));
        //true
        boolean result3 = org.apache.commons.collections.CollectionUtils.isNotEmpty(users3);

3.Map判断是否为空

        Map<String, Object> map1 = null;
        //false
        boolean result1 = org.apache.commons.collections.MapUtils.isNotEmpty(map1);

        Map<String, Object> map2 = new HashMap<>();
        //false
        boolean result2 = org.apache.commons.collections.MapUtils.isNotEmpty(map2);

        Map<String, Object> map3 = new HashMap<>();
        map2.put("test", "test");
        //true
        boolean result3 = org.apache.commons.collections.MapUtils.isNotEmpty(map3);

使用MapUtils工具类需导入依赖如下,版本号自己控制

        >
            >commons-collections>
            >commons-collections>
            >3.2.2>
        >