java8兩個List集合取交集、並集、差集、去重並集

java8兩個List集合取交集、並集、差集、去重並集

import java.util.ArrayList; import java.util.List; import static java.util.stream.Collectors.toList; public class Test { public static void main(String[] args) { List<String> list1 = new ArrayList<String>(); list1.add("1"); list1.add("2"); list1.add("3"); list1.add("5"); list1.add("6"); List<String> list2 = new ArrayList<String>(); list2.add("2"); list2.add("3"); list2.add("7"); list2.add("8"); // 交集
        List<String> intersection = list1.stream().filter(item -> list2.contains(item)).collect(toList()); System.out.println("---交集 intersection---"); intersection.parallelStream().forEach(System.out :: println); // 差集 (list1 - list2)
        List<String> reduce1 = list1.stream().filter(item -> !list2.contains(item)).collect(toList()); System.out.println("---差集 reduce1 (list1 - list2)---"); reduce1.parallelStream().forEach(System.out :: println); // 差集 (list2 - list1)
        List<String> reduce2 = list2.stream().filter(item -> !list1.contains(item)).collect(toList()); System.out.println("---差集 reduce2 (list2 - list1)---"); reduce2.parallelStream().forEach(System.out :: println); // 並集
        List<String> listAll = list1.parallelStream().collect(toList()); List<String> listAll2 = list2.parallelStream().collect(toList()); listAll.addAll(listAll2); System.out.println("---並集 listAll---"); listAll.parallelStream().forEachOrdered(System.out :: println); // 去重並集
        List<String> listAllDistinct = listAll.stream().distinct().collect(toList()); System.out.println("---得到去重並集 listAllDistinct---"); listAllDistinct.parallelStream().forEachOrdered(System.out :: println); System.out.println("---原來的List1---"); list1.parallelStream().forEachOrdered(System.out :: println); System.out.println("---原來的List2---"); list2.parallelStream().forEachOrdered(System.out :: println); } }