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list 按照元素的某個字段去重

1@Data
2@AllArgsConstructor
3@NoArgsConstructor
4public class Student {
5private Integer age;
6private String name;
7}

測試數據

1List<Student> studentList = Lists.newArrayList();
2studentList.add(new Student(28, "river"));
3studentList.add(new Student(12, "lucy"));
4studentList.add(new Student(33, "frank"));
5studentList.add(new Student(33, "lucy"));

java8 通過tree set 去重

1List<Student> studentDistinctList = studentList.stream()
2.collect(Collectors.collectingAndThen
3(Collectors.toCollection(() ->
4new TreeSet<>(Comparator.comparing(t -> t.getName()))),
5ArrayList::new
6)
7);
8System.out.println(new Gson().toJson(studentDistinctList));

擴展distinct 方法去重

1List<Student> studentDistinct2List = studentList.stream().filter(StreamUtil.distinctByKey(t->t.getName()))
2.collect(Collectors.toList());
3System.out.println(new Gson().toJson(studentDistinct2List));

工具類

01public class StreamUtil {
02/**
03* https://stackoverflow.com/questions/23699371/java-8-distinct-by-property
04* @param keyExtractor
05* @param <T>
06* @return
07*/
08public static <T> Predicate<T> distinctByKey(Function<? super T, ?> keyExtractor) {
09Set<Object> seen = ConcurrentHashMap.newKeySet();
10return t -> seen.add(keyExtractor.apply(t));
11}
12}