Java8 stream 求两个List集合取交集、并集、差集、去重并集

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