Lambda表达式,List对象集合去重

1.创建实体

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class EmployeeDto {
    private String id;
    private String name;
    private String no_id;
    private String dept;
    private int year;
    private EmpInfoPo info;
}

　　

2.List实体数据

{"dept":"研发部1","id":"001","name":"员工1号","no_id":"YF001","year":2}
{"dept":"研发部2","id":"002","name":"员工2号","no_id":"YF001","year":5}
{"dept":"研发部3","id":"003","name":"员工3号","no_id":"YF001","year":7}
{"dept":"研发部4","id":"004","name":"员工4号","no_id":"YF001","year":6}
{"dept":"研发部5","id":"005","name":"员工5号","no_id":"YF001","year":4}
{"dept":"研发部6","id":"006","name":"员工1号","no_id":"YF001","year":2}

　　

3.Lambda方式去重

集合方式排序、stream方式排序对比
Collectors.collectingAndThen()数据流转处理函数
distinctByKey()自定义比较器

	/**
     * 函数去重  利用TreeSet无重复特性
     * collect 收集器
     * Collectors 收集器的方法
     */
    public static void exceptRepeatV1(List<EmployeeDto> employeeList){
        ArrayList<EmployeeDto> collect = employeeList
                .stream()
                .collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(EmployeeDto::getName))), ArrayList::new));
        print(collect);
    }

    /**
     * 自定义方式去重
     * @param employeeList
     */
    public static void exceptRepeatV2(List<EmployeeDto> employeeList){
        List<EmployeeDto> collect = employeeList.stream()
                .filter(distinctByKey(e -> e.getName()))
                .collect(Collectors.toList());
        print(collect);
    }

    /**
     * 自定义比较方法
     * @param keyExtractor
     * @param <T>
     * @return
     */
    private static <T> Predicate<T> distinctByKey(Function<? super T,?> keyExtractor){
        Map<Object,Boolean> map=new ConcurrentHashMap<>();
        return t -> map.putIfAbsent(keyExtractor.apply(t),Boolean.TRUE)==null;
    }

　　

转载自：https://blog.csdn.net/Oaklkm/article/details/127074712