Java 集合多条件多规则排序 升序 降序 空值处理

Posted 2022-12-15 抓手

import com.google.common.collect.Lists;
import lombok.AllArgsConstructor;
import lombok.Data;

import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;

/**
 * @author 向振华
 * @date 2022/12/01 18:18
 */
public class Test 

    @Data
    @AllArgsConstructor
    public static class Shop 
        private String name;
        private Double price;
        private Integer count;
    

    public static void main(String[] args) 
        // 创建参数
        List<Shop> list = Lists.newArrayList(
                new Shop("1", 3.3, 10),
                new Shop("2", null, 30),
                new Shop("3", 4.4, 20),
                new Shop("4", 6.6, null),
                new Shop("5", 8.8, 20),
                new Shop("6", 8.8, 20),
                new Shop("7", 7.7, 60),
                new Shop("8", 7.7, 60)
        );

        // 多排序条件
        List<Shop> orderShopList = list.stream().sorted(Comparator
                // 先按数量降序（由于是降序，nullsFirst()方法会将null值放在后面）
                .comparing(Shop::getCount, Comparator.nullsFirst(Integer::compareTo).reversed())
                // 然后按价格升序（由于是升序，nullsFirst()方法会将null值放在前面）
                .thenComparing(Shop::getPrice, Comparator.nullsFirst(Double::compareTo))
                // 然后按名称降序（如果不设置null值排序规则，字段为null会报错）
                .thenComparing(Shop::getName, Comparator.reverseOrder())
        ).collect(Collectors.toList());

        // 打印排序结果
        orderShopList.forEach(System.out::println);
    

输出结果

Test.Shop(name=8, price=7.7, count=60)
Test.Shop(name=7, price=7.7, count=60)
Test.Shop(name=2, price=null, count=30)
Test.Shop(name=3, price=4.4, count=20)
Test.Shop(name=6, price=8.8, count=20)
Test.Shop(name=5, price=8.8, count=20)
Test.Shop(name=1, price=3.3, count=10)
Test.Shop(name=4, price=6.6, count=null)