Java-ArrayList去重问题

List自身去重

List<HtPersonDto> list = new ArrayList<>();
for (int i = 0; i < list.size() - 1; i++) {
   for (int j = list.size() - 1; j > i; j--) {
       if (list.get(j).getId().equals(list.get(i).getId())) {
          list.remove(j);
       }
   }
}

两个List去重

List<HtEventPersonInfoMap> htEventPersonInfoMapList = new ArrayList<>();
List<HtEventPersonInfoMap> existList = new ArrayList<>();
// htEventPersonInfoMapList中排除掉existList里面id相同的实体类
List<HtEventPersonInfoMap> delList = htEventPersonInfoMapList
        .stream()
        .filter(notComment -> 
                !existList
                        .stream()
                        .map(all -> all.getId()).collect(Collectors.toList()).contains(notComment.getId()))
        .collect(Collectors.toList());

其他

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());
 
        // 差集 (list1 - list2)
        List<String> reduce1 = list1.stream().filter(item -> !list2.contains(item)).collect(toList());
 
        // 差集 (list2 - list1)
        List<String> reduce2 = list2.stream().filter(item -> !list1.contains(item)).collect(toList());
 
        // 并集
        List<String> listAll = list1.parallelStream().collect(toList());
        List<String> listAll2 = list2.parallelStream().collect(toList());
        listAll.addAll(listAll2);
 
        // 去重并集
        List<String> listAllDistinct = listAll.stream().distinct().collect(toList());
        listAllDistinct.parallelStream().forEachOrdered(System.out :: println);
 
    }