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  • Steam之两个list间交集、并集、差集

    public static void main(String[] args) {
    List<String> list1 = new ArrayList();
    list1.add("1111");
    list1.add("2222");
    list1.add("3333");

    List<String> list2 = new ArrayList();
    list2.add("3333");
    list2.add("4444");
    list2.add("5555");

    // 交集
    List<String> intersection = list1.stream().filter(item -> list2.contains(item)).collect(Collectors.toList());
    System.out.println("---得到交集 intersection---");
    intersection.parallelStream().forEach(System.out :: println);

    // 差集 (list1 - list2)
    List<String> reduce1 = list1.stream().filter(item -> !list2.contains(item)).collect(Collectors.toList());
    System.out.println("---得到差集 reduce1 (list1 - list2)---");
    reduce1.parallelStream().forEach(System.out :: println);

    // 差集 (list2 - list1)
    List<String> reduce2 = list2.stream().filter(item -> !list1.contains(item)).collect(Collectors.toList());
    System.out.println("---得到差集 reduce2 (list2 - list1)---");
    reduce2.parallelStream().forEach(System.out :: println);

    // 并集
    List<String> listAll = list1.parallelStream().collect(Collectors.toList());
    List<String> listAll2 = list2.parallelStream().collect(Collectors.toList());
    listAll.addAll(listAll2);
    System.out.println("---得到并集 listAll---");
    listAll.parallelStream().forEach(System.out :: println);

    // 去重并集
    List<String> listAllDistinct = listAll.stream().distinct().collect(Collectors.toList());
    System.out.println("---得到去重并集 listAllDistinct---");
    listAllDistinct.parallelStream().forEach(System.out :: println);

    System.out.println("---原来的List1---");
    list1.parallelStream().forEach(System.out :: println);
    System.out.println("---原来的List2---");
    list2.parallelStream().forEach(System.out :: println);

    // 一般有filter 操作时,不用并行流parallelStream ,如果用的话可能会导致线程安全问题
      //判断对象要重写hash

    }
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  • 原文地址:https://www.cnblogs.com/TimeSay/p/11304792.html
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