java lambda List 分组 Collectors.groupingBy-526互联

package lambda.list;

import lombok.extern.slf4j.Slf4j;
import org.junit.Test;
import pojo.Dome;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

/**
 * @Author: xxx
 * @date 2021/5/14
 **/
@Slf4j
public class GroupTest {

    /***
     * 初始化测试数组
     * @date 2021/5/14
     **/

    private List<Dome> initArray() {
        Dome dome1 = new Dome("张三", 11.0, 10);
        Dome dome2 = new Dome("李四", 61.0, 11);
        Dome dome3 = new Dome("王五", 26.0, 12);
        Dome dome4 = new Dome("张三", 14.0, 14);
        Dome dome5 = new Dome("王五", 24.0, 15);
        Dome dome6 = new Dome("李四", 16.0, 16);
        Dome dome7 = new Dome("赵六", 35.0, 17);

        List<Dome> domes = new ArrayList<>();

        domes.add(dome1);
        domes.add(dome2);
        domes.add(dome3);
        domes.add(dome4);
        domes.add(dome5);
        domes.add(dome6);
        domes.add(dome7);

        log.info("domes : {}", domes);

        return domes;
    }

    /***
     * List分组
     * @date 2021/5/13
     **/

    @Test
    public void groupTest() {
        List<Dome> domes = initArray();

        Map<String, List<Dome>> collect = domes.stream().collect(Collectors.groupingBy(Dome::getName));

        log.info(" ================================================ ");

        for (String s : collect.keySet()) {
            log.info(" {} -> {}", s, collect.get(s));
        }

        log.info(" ================================================ ");

        for (Map.Entry<String, List<Dome>> stringListEntry : collect.entrySet()) {
            log.info(" {} -> {}", stringListEntry.getKey(), stringListEntry.getValue());
        }

/*
domes : [Dome{name='张三', money=11.0, age=10}, Dome{name='李四', money=61.0, age=11}, Dome{name='王五', money=26.0, age=12}, Dome{name='张三', money=14.0, age=14}, Dome{name='王五', money=24.0, age=15}, Dome{name='李四', money=16.0, age=16}, Dome{name='赵六', money=35.0, age=17}]
 ================================================
 李四 -> [Dome{name='李四', money=61.0, age=11}, Dome{name='李四', money=16.0, age=16}]
 张三 -> [Dome{name='张三', money=11.0, age=10}, Dome{name='张三', money=14.0, age=14}]
 王五 -> [Dome{name='王五', money=26.0, age=12}, Dome{name='王五', money=24.0, age=15}]
 赵六 -> [Dome{name='赵六', money=35.0, age=17}]
 ================================================
 李四 -> [Dome{name='李四', money=61.0, age=11}, Dome{name='李四', money=16.0, age=16}]
 张三 -> [Dome{name='张三', money=11.0, age=10}, Dome{name='张三', money=14.0, age=14}]
 王五 -> [Dome{name='王五', money=26.0, age=12}, Dome{name='王五', money=24.0, age=15}]
 赵六 -> [Dome{name='赵六', money=35.0, age=17}]
*/
    }
}