JAVA lambada表达式查询分组中的最大值

查询出每个班级年龄最大的学生和年龄最小的学生

//
public class MaxByMinBy {
    public static void main(String[] args) {
        Student student = new Student("Bruce", 27, "A");
        Student student1 = new Student("Michael", 23, "A");
        Student student2 = new Student("Lee", 22, "B");
        Student student3 = new Student("Lucy", 25, "B");
        List<Student> students = Arrays.asList(student, student1, student2, student3);
        Comparator<Student> ageComparator = Comparator.comparing(Student::getAge);
// 查询年纪最小 使用 minBy
        Map<String, Optional<Student>> collect = students.stream().collect(Collectors.groupingBy(Student::getClassName, Collectors.reducing(BinaryOperator.maxBy(ageComparator))));
        collect.forEach((k, v) -> System.out.println("Class:" + k + " Age:" + v.get().getAge() + " Name:" + v.get().getName()));
    }

    @Data
    @AllArgsConstructor
    static class Student {
        private String name;
        private Integer age;
        private String className;

    }
}

运行结果

Class:A Age:27 Name:Bruce
Class:B Age:25 Name:Lucy