2个list取交集_角的集合如何取交集

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);
// 并集
List<String> listAll = list1.parallelStream().collect(toList());
List<String> listAll2 = list2.parallelStream().collect(toList());
listAll.addAll(listAll2);
System.out.println("---并集 listAll---");
listAll.parallelStream().forEachOrdered(System.out :: println);
// 去重并集
List<String> listAllDistinct = listAll.stream().distinct().collect(toList());
System.out.println("---得到去重并集 listAllDistinct---");
listAllDistinct.parallelStream().forEachOrdered(System.out :: println);
System.out.println("---原来的List1---");
list1.parallelStream().forEachOrdered(System.out :: println);
System.out.println("---原来的List2---");
list2.parallelStream().forEachOrdered(System.out :: println);
}
}

private static <T> Predicate<T> distinctByKey(Function<? super T, Object> keyExtractor) { 

Map<Object, Boolean> seen = new ConcurrentHashMap<>();
return t -> seen.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
}
public static void main(String[] args) { 

List<String> list=new ArrayList<>();
list.add(1);
list.add(2);
list.add(3);
list.add(4);
List<Integer> list2=new ArrayList<>();
list.add(1);
list.add(6);
list.add(6);
list.add(7);
list.addAll(list2);
list = list.stream().filter(distinctByKey(Integer::intValue)).collect(Collectors.toList());
System.out.println(list);
}