Java8中怎么用Lambda遍历两个List匹配数据

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Lambda遍历两个List匹配数据

1. 定义一个静态方法

/**
     *  通过遍历两个List中按id属性相等的归结到resultList中
     * @param oneList
     * @param twoList
     */
    public static List<Map<Object, Object>> compareListHitData(List<Map<Object, Object>> oneList, List<Map<Object, Object>> twoList) {
        List<Map<Object, Object>> resultList = oneList.stream().map(map -> twoList.stream()
                .filter(m -> Objects.equals(m.get("id"), map.get("id")))
                .findFirst().map(m -> {
                    map.putAll(m);
                    return map;
                }).orElse(null))
                .filter(Objects::nonNull).collect(Collectors.toList());
        return resultList;
    }

2. Main方法测试

public static void main(String[] args) {
        List<Map<Object, Object>> oneList = new ArrayList<>();
        Map<Object, Object> oneMap = new HashMap<>();
        oneMap.put("id", 111);
        oneMap.put("userName", "何金荣");
        Map<Object, Object> twoMap = new HashMap<>();
        twoMap.put("id", 222);
        twoMap.put("userName", "Hejinrong");
        oneList.add(oneMap);
        oneList.add(twoMap);
        List<Map<Object, Object>> twoList = new ArrayList<>();
        Map<Object, Object> threeMap = new HashMap<>();
        threeMap.put("id", 111);
        threeMap.put("userName", "何金荣");
        Map<Object, Object> fourMap = new HashMap<>();
        fourMap.put("id", 333);
        fourMap.put("userName", "Hejinrong");
        twoList.add(threeMap);
        twoList.add(fourMap);
        List<Map<Object, Object>> resultList = compareListHitData(oneList, twoList);
        System.out.println(resultList);
    }

3. 输出结果

jdk1.8的stream对两个List遍历匹配数据的处理

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;
 
public class testStream {
    public static void main(String[] args) {
        List<AwardInfo> prizeRecords = new ArrayList<AwardInfo>(6);
        List<StockInfo> stockDTOList = new ArrayList<StockInfo>();
        for (int i = 0; i < 6; i++) {
            AwardInfo AwardInfo = new AwardInfo();
            AwardInfo.setStockNo((i+1)+"");
            prizeRecords.add(AwardInfo);
        }
        for (int i = 0; i < 3; i++) {
            StockInfo stockDTO = new StockInfo();
            stockDTO.setStockNo((i+1)+"");
            stockDTO.setThirdStockNo("third"+(i+1));
            stockDTOList.add(stockDTO);
        }
        StockInfo stockDTO1 = new StockInfo();
        stockDTO1.setStockNo((44)+"");
        stockDTO1.setThirdStockNo("third"+44);
        stockDTOList.add(stockDTO1);
 
        StockInfo stockDTO2 = new StockInfo();
        stockDTO2.setStockNo((55)+"");
        stockDTO2.setThirdStockNo("third"+55);
        stockDTOList.add(stockDTO2);
 
        //prizeRecords与stockDTOList求差集
        List<AwardInfo> resultList1 = prizeRecords.stream()
                .map(map -> stockDTOList.stream()
                        .filter(m -> !Objects.equals(m.getStockNo(), map.getStockNo()))
                        .findFirst().map(m -> {
                            return map;
                        }).orElse(null))
                .filter(Objects::nonNull).collect(Collectors.toList());
        /**
         * 求差集：失败结果参考
         * [AwardInfo{userId='null', stockNo='1', thirdStockNo='null'},
         * AwardInfo{userId='null', stockNo='2', thirdStockNo='null'},
         * AwardInfo{userId='null', stockNo='3', thirdStockNo='null'},
         * AwardInfo{userId='null', stockNo='4', thirdStockNo='null'},
         * AwardInfo{userId='null', stockNo='5', thirdStockNo='null'},
         * AwardInfo{userId='null', stockNo='6', thirdStockNo='null'}]
         */
        System.out.println(resultList1.toString());
 
 
       /* List<AwardInfo> list2 = prizeRecords.stream()
                .filter(map -> stockDTOList.stream().anyMatch(map1 -> map.getStockNo().equals(map1.getStockNo())))
                .forEach(map -> {
                    map.setThirdStockNo(map1.getThirdStockNo());
                });*/
        List<AwardInfo> resultList2 = prizeRecords.stream().map(m->{
            stockDTOList.stream().filter(m2->Objects.equals(m.getStockNo(), m2.getStockNo()))
                    .forEach(s-> m.setThirdStockNo(s.getThirdStockNo()));
            return m;
        }).collect(Collectors.toList());
        /**
         * stockNo=4,5,6的结果没去掉！
         * [AwardInfo{userId='null', stockNo='1', thirdStockNo='third1'},
         * AwardInfo{userId='null', stockNo='2', thirdStockNo='third2'},
         * AwardInfo{userId='null', stockNo='3', thirdStockNo='third3'},
         * AwardInfo{userId='null', stockNo='4', thirdStockNo='null'},
         * AwardInfo{userId='null', stockNo='5', thirdStockNo='null'},
         * AwardInfo{userId='null', stockNo='6', thirdStockNo='null'}]
         */
        System.out.println(resultList2.toString());
 
        List<AwardInfo> list3 = prizeRecords.stream()
                .map(map -> stockDTOList.stream()
                        .filter(m -> Objects.equals(m.getStockNo(), map.getStockNo()))
                        .findFirst().map(m -> {
                            map.setThirdStockNo(m.getThirdStockNo());
                            return map;
                        }).orElse(null))
                .filter(Objects::nonNull).collect(Collectors.toList());
        /**
         * stockNo=4,5,6的结果已去掉
         * [AwardInfo{userId='null', stockNo='1', thirdStockNo='third1'},
         * AwardInfo{userId='null', stockNo='2', thirdStockNo='third2'},
         * AwardInfo{userId='null', stockNo='3', thirdStockNo='third3'}]
         */
        System.out.println(list3.toString());
    }
    static class StockInfo{
        private String stockNo;
        private String stockName;
        private String thirdStockNo; 
        public String getStockNo() {
            return stockNo;
        }
 
        public void setStockNo(String stockNo) {
            this.stockNo = stockNo;
        }
 
        public String getStockName() {
            return stockName;
        }
 
        public void setStockName(String stockName) {
            this.stockName = stockName;
        }
 
        public String getThirdStockNo() {
            return thirdStockNo;
        }
 
        public void setThirdStockNo(String thirdStockNo) {
            this.thirdStockNo = thirdStockNo;
        }
 
        @Override
        public String toString() {
            return "StockInfo{" +
                    "stockNo='" + stockNo + '\'' +
                    ", stockName='" + stockName + '\'' +
                    ", thirdStockNo='" + thirdStockNo + '\'' +
                    '}';
        }
    }
    static class AwardInfo{       
        private String userId;       
        private String stockNo;        
        private String thirdStockNo; 
        public String getUserId() {
            return userId;
        }
 
        public void setUserId(String userId) {
            this.userId = userId;
        }
 
        public String getStockNo() {
            return stockNo;
        }
 
        public void setStockNo(String stockNo) {
            this.stockNo = stockNo;
        }
 
        public String getThirdStockNo() {
            return thirdStockNo;
        }
 
        public void setThirdStockNo(String thirdStockNo) {
            this.thirdStockNo = thirdStockNo;
        }
 
        @Override
        public String toString() {
            return "AwardInfo{" +
                    "userId='" + userId + '\'' +
                    ", stockNo='" + stockNo + '\'' +
                    ", thirdStockNo='" + thirdStockNo + '\'' +
                    '}';
        }
    }
}

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