JAVA实验五optional

只用写Test类其他类都给了

package com.experiment05.Test;
import com.experiment05.entity.College;
import com.experiment05.entity.Student;
import com.experiment05.entity.Teacher;
import com.experiment05.resource.DatabaseUtils;

import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

public class Test {
    public static void main(String[] args) {
         System.out.println(getCourseName(DatabaseUtils.getStudents(),8888));
         printCollegeName(DatabaseUtils.getStudents(), 201001, 1002);
    }

    
    private static String getCourseName(List students, int sNumber) {
        return  students.stream()
                .filter(a -> a.getNumber() == sNumber)//筛选
                .collect(Collectors.toList())
                .stream()
                .findFirst()
                .map(Student::getTeacher)
                .map(Teacher::getCollege)
                .map(College::getName)
                .orElse(null);

    }

    
    private static void printCollegeName(List students, int sNumber, int tNumber) {
        System.out.println(students.stream()
                .filter(a -> a.getNumber() == sNumber)
                .collect(Collectors.toList())
                .stream()
                .findFirst()
                .map(Student::getTeacher)
                .filter(a -> a.getNumber() == tNumber)
                .map(Teacher::getCollege)
                .map(College::getName)
                .orElse(null));
    }

}