Java对list动态排序_java对list 动态排序

期望：动态的根据某个属性进行排序

目录

 方案一：

1.创建User对象

2.实现自定义排序工具类

3.test

4.输出结果展示

方案二：

1.创建User对象

2.实现自定义排序工具类

3.test

4.输出结果展示

 方案一：

1.创建User对象

@Data
public class User  {
 
    private Integer id;
 
    private String name;
 
    private Integer age;
 
 
}

2.实现自定义排序工具类

MyCompare

@Data
public class MyCompare<T> implements Comparator<T> {
 
    private String param;
 
    private Boolean flag;
 
    private Comparator<Object> comparator;
 
    public MyCompare(String param, Boolean flag) {
        this.setParam(param);
        this.setFlag(flag);
        this.comparator = new RealCompare<>();
    }
 
    @Override
    public int compare(T o1, T o2) {
        try {
            Object value1 = PropertyUtils.getProperty(o1, this.param);
            Object value2 = PropertyUtils.getProperty(o2, this.param);
 
            if (value1 == null) {
                return 1;
            }
            if (value2 == null) {
                return -1;
            }
 
            Comparator<Object> comparator = this.comparator;
            return flag ? comparator.compare(value1, value2) : -comparator.compare(value1, value2);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return 0;
    }
}

RealCompare

public class RealCompare<T> implements Comparator<T> {
 
    @Override
    public int compare(Object obj1, Object obj2) {
        if (obj1 == null) {
            return 1;
        }
        if (obj2 == null) {
            return -1;
        }
        return (int)obj1 - (int)obj2;
    }
}

3.test

public static void main(String[] args) {
        User u1 = new User();
        u1.setId(10);
        u1.setName("aaa");
        u1.setAge(18);
        User u3 = new User();
//        u3.setId(12);
        u3.setName("bbb");
        u3.setAge(20);
        User u2 = new User();
        u2.setId(11);
        u2.setName("ccc");
        u2.setAge(19);
 
        List<User> list = new ArrayList<>();
        list.add(u1);
        list.add(u2);
        list.add(u3);
 
        //按照id进行排序，false表示降序
        List<User> sortList = list.stream().sorted(new MyCompare<>("id",false)).collect(Collectors.toList());
        for (User user : id) {
            System.out.println(user);
        }
 
    }

4.输出结果展示

方案二：

1.创建User对象

@Data
public class User  {
 
    private Integer id;
 
    private String name;
 
    private Integer age;
 
 
}

2.实现自定义排序工具类

public class ListSortUtil {
 
    /**
     * 自定义字段排序
     *
     * @param list
     * @param sortName
     * @param desc
     * @param descNull
     * @return
     */
    public static <T> List<T> sortListByField(List<T> list, String sortName, boolean desc, boolean descNull, Class<T> tClass) {
        return list.stream()
                .map(convertBeanToMap())
                .sorted(getMapComparator(sortName, desc, descNull))
                .map(convertMapToBean(tClass))
                .collect(Collectors.toList());
    }
 
    public static <T> List<?> sortListByField(List<T> list, String sortName, boolean desc, Class<T> tClass) {
        return sortListByField(list, sortName, desc, true, tClass);
    }
 
    private static Comparator<Map<String, Object>> getMapComparator(String sortName, boolean desc, boolean descNull) {
        if (desc) {
            return ((Comparator<Map<String, Object>>) (o1, o2) -> getCompareUtil(sortName, descNull, o1, o2)).reversed();
        }
        return (o1, o2) -> getCompareUtil(sortName, descNull, o1, o2);
    }
    
    /**
     * 比较方法
     *
     * @param sortName 排序字段
     * @param descNull null值排序规则
     * @param o1
     * @param o2
     * @return
     */
    private static int getCompareUtil(String sortName, boolean descNull, Map<String, Object> o1, Map<String, Object> o2) {
        return CompareUtil.compare(o1.get(sortName), o2.get(sortName), descNull);
    }
 
 
    private static <T> Function<Map<String, Object>, T> convertMapToBean(Class<T> tClass) {
        return map -> BeanUtil.toBean(map, tClass);
    }
 
    private static <T> Function<T, Map<String, Object>> convertBeanToMap() {
        return BeanUtil::beanToMap;
    }
}

3.test

public static void main(String[] args) {
        User u1 = new User();
        u1.setId(10);
        u1.setName("aaa");
        u1.setAge(18);
        User u3 = new User();
//        u3.setId(12);
        u3.setName("bbb");
        u3.setAge(20);
        User u2 = new User();
        u2.setId(11);
        u2.setName("ccc");
        u2.setAge(19);
 
        List<User> list = new ArrayList<>();
        list.add(u1);
        list.add(u2);
        list.add(u3);
 
        //按照id进行排序，desc为false表示升序，descNull为false表示null值排到最后面
        List<User> id = ListSortUtil.sortListByField(list, "id", false, false, User.class);
 
        for (User user : id) {
            System.out.println(user);
        }
 
    }

4.输出结果展示