java8 groupby 对多个字段进行去重, 统计 partitioningBy

package com.icil.elsa.test.utils;

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

import org.junit.Test;

import lombok.ToString;
import lombok.Data;



/**
 * 用 java8 对 list 按照多个字段进行去重 id  ,  message ,orderNO 去重
 * 对对象 MilestonesValidTO 按照 field 
 * 参考1:https://blog.csdn.net/robotfive/article/details/89200294
 * 参考2:https://blog.csdn.net/weixin_39643007/article/details/90511098 
 * @throws Exception
 */
public class GroupBYTest {
    
    
    @Data
    @ToString
    public class MilestonesValidTO {
        private String id;
        
        private String message;
        
        private String orderNO;
        
        private String courierBillNo;
        
        private String status;
        
        public MilestonesValidTO(String id, String message, String orderNO, String courierBillNo) {
            super();
            this.id = id;
            this.message = message;
            this.orderNO = orderNO;
            this.courierBillNo = courierBillNo;
        }
        }


    /**
　　　　　#####如果 id + message + orderNo 都一样， 就认为是一条数据#######

     * 用 java8 对 list 按照多个字段进行去重 id  ,  message ,orderNO 去重
     * 对对象 MilestonesValidTO 按照 field 
     * 如果仅仅是去重,推荐使用方式1
     * @throws Exception
     */
     /*################# 方式1: 直接重写 comparater 方法  ####################*/
    @Test
    public void testGroupByMutilFiled1() throws Exception {
        
        ArrayList<MilestonesValidTO> list = new ArrayList<MilestonesValidTO>();
        list.add(new MilestonesValidTO("1","A","sea","2341"));
        list.add(new MilestonesValidTO("1","A","sea","2341"));
        list.add(new MilestonesValidTO("3","B","sea","2341"));
        list.add(new MilestonesValidTO("4","A","sea","2341"));
        list.add(new MilestonesValidTO("5","C","sea","2341"));
        

        List<MilestonesValidTO> lst = list.parallelStream().collect(Collectors.collectingAndThen(Collectors.toCollection(
                    () -> new TreeSet<>(Comparator.comparing(o -> o.getId() + "#" + o.getMessage() + "#" + o.getOrderNO()))),
                    ArrayList<MilestonesValidTO>::new));
        
         lst.forEach(m-> System.err.println(m.toString()));
    }
    
    /**
     * 用 java8 对 list 按照多个字段进行去重 id  ,  message ,orderNO 去重
     * 对对象 MilestonesValidTO 按照 field 
     * 方式2:用于收集,统计,比较合适
     * @throws Exception
     */
     /*################# 方式2: Collectors.groupingBy(内嵌groupBy)   ####################*/
    @Test
    public void testGroupByMutilFiled2() throws Exception {
        
        ArrayList<MilestonesValidTO> list = new ArrayList<MilestonesValidTO>();
        list.add(new MilestonesValidTO("1","A","sea","2341"));
        list.add(new MilestonesValidTO("1","A","sea","2341"));
        list.add(new MilestonesValidTO("3","B","sea","2341"));
        list.add(new MilestonesValidTO("4","A","sea","2341"));
        list.add(new MilestonesValidTO("5","C","sea","2341"));
        
        
//        Map<String, Map<String, Double>> sumCase = statisticalAnalyses.stream()
//                .collect(Collectors.groupingBy(
//                        StatisticalAnalysis::getCreateTime,
//                        Collectors.groupingBy(StatisticalAnalysis::getHandlingDepartmentName, Collectors.summingDouble(StatisticalAnalysis::getSimplePenaltyAmount))));

        Map<String, Map<String, List<MilestonesValidTO>>> collect = list.parallelStream()
        .collect(Collectors.groupingBy(MilestonesValidTO::getId,Collectors.groupingBy(MilestonesValidTO::getMessage)));
        
        
        collect.forEach((k,v)->{System.err.println("K->"+k+"   V-->"+v);});
    }
}

 

常用：

//提取Bean 中的个别字段
List<String> hbookingNo = houseLinkList.stream().map(MasterLinkDO::getBookingNo).collect(Collectors.toList());




//把一个大的list切割
List<List<String>> ListbookingNoList = Lists.partition(bookingNoList, 100);



 //过滤去重

List<MilestoneInfo> successAndDistincList = worktbMileAllList.stream().filter(m->m.getSuccess()==true).collect(Collectors.collectingAndThen(Collectors.toCollection(
// () -> new TreeSet<>(Comparator.comparing(o -> o.getCourierBillNo()))),
() -> new TreeSet<>(Comparator.comparing(o -> o.getStatus() + "#" + o.getBookingNo() + "#" + o.getCourierBillNo()))),
ArrayList<MilestoneInfo>::new));

            
 //分组
Map<String, Map<String, List<MilestoneInfo>>> status_bookingNoAndDetailMap_map = worktbMileSuccessAndDistincList.stream()
        .collect(Collectors.groupingBy(MilestoneInfo::getStatus,Collectors.groupingBy(MilestoneInfo::getBookingNo)));
                
    

 

 partitioningBy:

有这样一个集合：

List<Integer> integers = [ 1,2,3,4,5,6,7,8,9]
现在需要把集合按奇偶数分割为两个列表。这种情况下，我们可以使用Collectors.partitioningBy来分割：

Map<Boolean, List<Integer>> map = 
    integers.stream().collect(Collectors.partitioningBy(x -> x%2 == 0));
partitioningBy会根据值是否为true，把集合分割为两个列表，一个true列表，一个false列表。