NEFU-2023-JAVA实验五

男娘i 2024-04-17 11:43 92阅读 0赞

题目

> 实验五 Optional操作实验  
> 实验目的  
> 理解解决Java空指针异常的重要性  
> 掌握Optional对空引用的基本操作方法  
> 掌握基于Optional的函数式编程  
> 掌握整合集合Stream与Optional的操作方法  
>   
> 实验内容  
> 创建实验项目工程java-experiments  
> 在com.experiment05.entity下，创建以下实体类  
> College实体类，包含学院名称  
> Teacher实体类，包含教师工号，姓名，及所属学院  
> Student实体类，包含学号，姓名，年级，指导教师  
>   
> 在com.experiment05.resource下，创建DatabaseUtils类  
> 模拟2个学院，2名教师，4名学生。模拟信息封装到各对象，创建一个学生集合封装所有学生测试。
> 
> ####  ####
> 
> 基于Optional，按需求实现测试类Test中的方法，模拟正确/错误数据信息验证代码的有效性。
> 
> （1）提交Test类的代码。（其它类的代码已给）；
> 
> （2）提交测试代码的运行截图；
> 
> （3）说明实验中出现的问题和解决过程，写出实验的心得体会。

com.experiment05.entity

package com.experiment05.entity;
    
    public class College {
        private String name;
    
        public College(String name) {
            this.name = name;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    }

package com.experiment05.entity;
    
    public class Student {
        private int number;
        private String name;
        private int year;
        private Teacher teacher;
    
        public Student(int number, String name, int year) {
            this.number = number;
            this.name = name;
            this.year = year;
        }
    
        public int getNumber() {
            return number;
        }
    
        public void setNumber(int number) {
            this.number = number;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public int getYear() {
            return year;
        }
    
        public void setYear(int year) {
            this.year = year;
        }
    
        public Teacher getTeacher() {
            return teacher;
        }
    
        public void setTeacher(Teacher teacher) {
            this.teacher = teacher;
        }
    }

package com.experiment05.entity;
    
    public class Teacher {
        private int number;
        private String name;
        private College college;
    
        public Teacher(int number, String name) {
            this.number = number;
            this.name = name;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public College getCollege() {
            return college;
        }
    
        public void setCollege(College college) {
            this.college = college;
        }
    
        public int getNumber() {
            return number;
        }
    
        public void setNumber(int number) {
            this.number = number;
        }
    }

com.experiment05.resource

package com.experiment05.resource;
    
    import java.util.ArrayList;
    import java.util.List;
    
    import com.experiment05.entity.College;
    import com.experiment05.entity.Student;
    import com.experiment05.entity.Teacher;
    
    public class DatabaseUtils {
        private static final List<Student> STUDENTS = create();
    
        private static List<Student> create() {
            College c1 = new College("信息学院");
            College c2 = new College("经济管理学院");
    
            Teacher t1 = new Teacher(1001, "吕惠玲");
            t1.setCollege(c1);
            Teacher t2 = new Teacher(1002, "曾志优");
            t2.setCollege(c2);
    
            Student s1 = new Student(201001,"赵阳阳", 2010);
            s1.setTeacher(t1);
            Student s2 = new Student(201002,"邵鹏", 2010);
            s2.setTeacher(t1);
            Student s3 = new Student(201103,"高学斌", 2011);
            s3.setTeacher(t2);
            Student s4 = new Student(201104,"张扬", 2011);
            s4.setTeacher(t2);
    
            List<Student> students = new ArrayList<>();
            students.add(s1); students.add(s2);
            students.add(s3); students.add(s4);
            return students;
        }
    
        public static List<Student> getStudents() {
            return STUDENTS;
        }
    
    
    
    }

test

package com.experiment05.test;
    
    import java.util.List;
    import java.util.Optional;
    import java.lang.String;
    
    import com.experiment05.entity.Student;
    import com.experiment05.entity.Teacher;
    import com.experiment05.resource.DatabaseUtils;
    
    public class Test {
        public static void main(String[] args) {
             getCollegeName(DatabaseUtils.getStudents().get(0));
             isTeacher(DatabaseUtils.getStudents().get(0), "曾志优");
             getCollegeName(DatabaseUtils.getStudents(),201001);
             printCollegeName(DatabaseUtils.getStudents(), 201001, 1002);
        }
    
        /**
         * 基于给定学生，获取学生的导师的所在学院名称。
         * 任何一项不存在或失败，返回 未知学院
         * @param student
         * @return
         */
        private static void getCollegeName(Student student) {
             Optional.ofNullable(student)
                    .map(Student::getTeacher)
                    .map(Teacher::getCollege)
                    .ifPresentOrElse(college -> System.out.println(college.getName()),() -> System.out.println("unknown"));
        }
    
        /**
         * 基于给定学生及教师姓名，判断是否为给定学生的指导教师。
         * 不匹配或不存在，均返回false
         * @param student
         * @param teacherName
         * @return
         */
        private static void isTeacher(Student student, String teacherName) {
            Optional.ofNullable(student)
                    .map(Student::getTeacher)
                    .filter(Teacher->Teacher.getName().equals(teacherName))
                    .ifPresentOrElse(Teacher -> System.out.println("true"),() -> System.out.println("false"));
        }
    
        /**
         * 基于给定学生集合，学生编号，实现获取学生的导师的所在学院名称。
         * 任何一项不存在或失败，返回 未知学院
         * 结合collection stream findFirst()方法实现
         * 可直接通过一条方法链实现
         *
         * @param students
         * @param sNumber
         * @return
         */
        private static void getCollegeName(List<Student> students, int sNumber) {
            students.stream()
                    .filter(student -> student.getNumber() == sNumber)
                    .findFirst()
                    .map(Student :: getTeacher)
                    .map(Teacher::getCollege)
                    .ifPresentOrElse(college -> System.out.println(college.getName()),()-> System.out.println("unknown"));
        }
    
        /**
         * 实现在给定学生集合中查询指定编号学生，如果学生导师编号为指定编号，打印显式导师所在学院名称。
         * 任何一项不存在或失败，打印显式 未知学院
         * 结合collection stream findFirst()方法实现
         * 可直接通过一条方法链实现
         *
         * @param students
         * @param sNumber，学生编号
         * @param tNumber，教师编号
         */
        private static void printCollegeName(List<Student> students, int sNumber, int tNumber) {
            students.stream()
                    .filter(student -> student.getNumber() == sNumber)
                    .filter(student -> student.getTeacher().getNumber() == tNumber)
                    .findFirst()
                    .map(Student::getTeacher)
                    .map(Teacher::getCollege)
                    .ifPresentOrElse(college -> System.out.println(college.getName()),() -> System.out.println("unknown"));
    
        }
    
    }