List＜Map＞ 多字段排序

package com.example.test;

import com.beust.jcommander.internal.Lists;
import com.beust.jcommander.internal.Maps;
import com.example.utils.DateUtil;
import org.junit.Test;

import java.util.*;
import java.util.stream.Collectors;

/**
 * @author
 * @Description
 * @create 2020-07-29 17:58
 */
public class CommonTest {

    class PojoTest {
        private int num;
        private Date date;

        public PojoTest(int num, Date date) {
            this.num = num;
            this.date = date;
        }

        public int getNum() {
            return num;
        }

        public void setNum(int num) {
            this.num = num;
        }

        public Date getDate() {
            return date;
        }

        public void setDate(Date date) {
            this.date = date;
        }

        @Override
        public String toString() {
            return "PojoTest{" +
                    "num=" + num +
                    ", date=" + date +
                    '}';
        }
    }

    @Test
    public void test() {
        List<PojoTest> pojos = Lists.newArrayList(
                new PojoTest(10, DateUtil.formatStringToDate("2020-07-30", "yyyy-MM-dd")),
                new PojoTest(10, DateUtil.formatStringToDate("2020-07-29", "yyyy-MM-dd")),
                new PojoTest(16, DateUtil.formatStringToDate("2020-07-28", "yyyy-MM-dd")),
                new PojoTest(16, DateUtil.formatStringToDate("2020-07-30", "yyyy-MM-dd")),
                new PojoTest(20, DateUtil.formatStringToDate("2020-07-31", "yyyy-MM-dd"))
        );
        System.err.println("===================0======================");
        // stream.sorted 类中单个字段排序
        List<PojoTest> pojoTests = pojos.stream().sorted(Comparator.comparing(PojoTest::getDate)).collect(Collectors.toList());
        pojoTests.forEach(System.err::println);
        System.err.println("===================1======================");
        // stream.sorted 类中单个字段排序
        pojoTests = pojos.stream().sorted(Comparator.comparing(PojoTest::getNum)).collect(Collectors.toList());
        pojoTests.forEach(System.err::println);
        System.err.println("===================2======================");
        // stream.sorted 类中多个字段排序
        pojoTests = pojos.stream().sorted(Comparator.comparing(PojoTest::getNum).thenComparing(PojoTest::getDate, Comparator.reverseOrder())).collect(Collectors.toList());
        pojoTests.forEach(System.err::println);
        System.err.println("===================3======================");
        // list.sort 类中多个字段排序
        pojos.sort(Comparator.comparing(PojoTest::getNum).thenComparing(PojoTest::getDate, Comparator.reverseOrder()));
        pojos.forEach(System.err::println);
        System.err.println("===================4======================");

        List<Map> maps = Lists.newArrayList(
                Maps.newHashMap("aa", 10, "bb", DateUtil.formatStringToDate("2020-07-30", "yyyy-MM-dd")),
                Maps.newHashMap("aa", 10, "bb", DateUtil.formatStringToDate("2020-07-29", "yyyy-MM-dd")),
                Maps.newHashMap("aa", 16, "bb", DateUtil.formatStringToDate("2020-07-28", "yyyy-MM-dd")),
                Maps.newHashMap("aa", 16, "bb", DateUtil.formatStringToDate("2020-07-30", "yyyy-MM-dd")),
                Maps.newHashMap("aa", 20, "bb", DateUtil.formatStringToDate("2020-07-31", "yyyy-MM-dd"))
        );
        // List<Map> 使用sorted排序时，单个字段排序没有问题, 但是使用thenComparing排序多个字段就会出现问题，似乎是无法确认类型的问题，详细原因我也不是太清楚，有大佬知道的话麻烦可以在评论里说下，谢谢
        maps = maps.stream().sorted(Comparator.comparing(a -> Long.parseLong(a.get("aa") + ""))).collect(Collectors.toList());
        maps.forEach(System.err::println);
        System.err.println("===================5======================");
        // maps = maps.stream().sorted(Comparator.comparing(a -> Long.parseLong(a.get("aa") + "")).thenComparing(Comparator.comparing(a -> (Date) a.get("bb"), Comparator.reverseOrder()))).collect(Collectors.toList());
        // 上面那种方式没法排序，但是直接使用list的sort排序却是可以的
        Comparator<Map> aa = Comparator.comparing(a -> Long.parseLong(a.get("aa") + ""));
        Comparator<Map> bb = Comparator.comparing(a -> (Date) a.get("bb"), Comparator.reverseOrder());
        maps.sort(aa.thenComparing(bb));
        maps.forEach(System.err::println);
    }
}

本文地址：https://blog.csdn.net/xiaodao0706/article/details/107688389