Java list去重 取重

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public class Test {     public static void main(String[] args) {         List<String> list = new ArrayList<>();         List<String> list2 = new ArrayList<>();         list.add("1");         list.add("1");         list.add("2");         list.add("2");         list.add("3");         List<String> collect = list.stream().filter(e -> {             boolean flag = !list2.contains(e); // 去重 //            boolean flag = list2.contains(e); // 取重             list2.add(e);             return flag;         }).collect(Collectors.toList());         System.out.println(collect);       } }