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> compareListHitData(List> oneList, List> twoList) {        List> 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> oneList = new ArrayList<>();        Map oneMap = new HashMap<>();        oneMap.put("id", 111);        oneMap.put("userName", "何金荣");        Map twoMap = new HashMap<>();        twoMap.put("id", 222);        twoMap.put("userName", "Hejinrong");        oneList.add(oneMap);        oneList.add(twoMap);        List> twoList = new ArrayList<>();        Map threeMap = new HashMap<>();        threeMap.put("id", 111);        threeMap.put("userName", "何金荣");        Map fourMap = new HashMap<>();        fourMap.put("id", 333);        fourMap.put("userName", "Hejinrong");        twoList.add(threeMap);        twoList.add(fourMap);        List> 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 prizeRecords = new ArrayList(6);        List stockDTOList = new ArrayList();        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 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 list2 = prizeRecords.stream()                .filter(map -> stockDTOList.stream().anyMatch(map1 -> map.getStockNo().equals(map1.getStockNo())))                .forEach(map -> {                    map.setThirdStockNo(map1.getThirdStockNo());                });*/        List 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 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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