Java8的Lambda遍歷兩個List匹配數據方式
Lambda遍歷兩個List匹配數據
1. 定義一個靜態方法
/** * 通過遍歷兩個List中按id屬性相等的歸結到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方法測試
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", "何金榮"); 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", "何金榮"); 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. 輸出結果
jdk1.8的stream對兩個List遍歷匹配數據的處理
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與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:失敗結果參考 * [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的結果沒去掉! * [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的結果已去掉 * [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 + '\'' + '}'; } } }
以上為個人經驗,希望能給大傢一個參考,也希望大傢多多支持WalkonNet。
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