如何实现java8 list按照元素的某个字段去重

list 按照元素的某个字段去重

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@Data @AllArgsConstructor @NoArgsConstructor public class Student { private Integer age; private String name; }

测试数据

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

java8 通过tree set 去重

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List<Student> studentDistinctList = studentList.stream() .collect(Collectors.collectingAndThen (Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(t -> t.getName()))), ArrayList::new ) ); System.out.println(new Gson().toJson(studentDistinctList));

扩展distinct 方法去重

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

工具类

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public class StreamUtil { /** * https://stackoverflow.com/questions/23699371/java-8-distinct-by-property * @param keyExtractor * @param <T> * @return */ public static <T> Predicate<T> distinctByKey(Function<? super T, ?> keyExtractor) { Set<Object> seen = ConcurrentHashMap.newKeySet(); return t -> seen.add(keyExtractor.apply(t)); } }