Java 集合与函数式编程

2021-12-28

集合与函数式编程实验

在com.experiment04.entity下，创建Student类，代码如下；
在com.experiment04.resource下，创建DatabaseUtils类，代码如下；
在com.experiment04.service下，创建StudentService接口，代码如下；
在com.experiment04.service.impl下，创建StudentService接口的实现类StudentServiceImpl，基于集合stream等操作，按接口方法注释需求实现

代码如下：

main

import com.experiment04.entity.Student;
import com.experiment04.service.StudentService;
import com.experiment04.service.impl.StudentServiceImpl;
public class main {
    public static void main(String[] args) {
        StudentService studentService=new StudentServiceImpl();
        StudentServiceImpl studentServiceShow(StudentServiceImpl)studentService;

        System.out.println("--------------1.向集合添加一个学生，返回当前全部学生----------------------");
        studentService.addStudent(new Student(201001, Student.Sex.FEMALE, "赵阳阳", 2010));
        studentService.addStudent(new Student(201002, Student.Sex.MALE, "邵鹏", 2010));
        studentService.addStudent(new Student(201103, Student.Sex.MALE, "高学斌", 2011));
        studentService.addStudent(new Student(201104, Student.Sex.MALE, "张扬", 2011));
        studentService.addStudent(new Student(201205, Student.Sex.FEMALE, "吕惠玲", 2012));
        studentService.addStudent(new Student(201206, Student.Sex.MALE, "曾志优", 2012));
        show
        studentServiceShow.studentList.forEach(u-> System.out.println(u.getId()+" "
        +u.getName()+" "
                +u.getYear()+" "
                +u.getSex()+" "
        ));


        2.返回指定届的全部学生
        System.out.println("---------------2.返回指定届的全部学生---------------------");
        studentService.listStudentsByYear(2010).forEach(u-> System.out.println(u.getId()+" "
                +u.getName()+" "
                +u.getYear()+" "
                +u.getSex()+" "
        ));
        ///3.返回指定届，指定性别的全部学生的姓名
        System.out.println("----------------3.返回指定届，指定性别的全部学生的姓名--------------------");
        studentService.listStudentsNames(2010, Student.Sex.MALE).forEach(u-> System.out.println(u));
        ///4.将所有学生，以性别分组
        System.out.println("----------------4.将所有学生，以性别分组--------------------");
        try {
            studentService.mapStudentsBySex().get(Student.Sex.MALE).forEach(u-> System.out.println(u.getId()+" "
                            +u.getName()+" "
                            +u.getYear()+" "
                            +u.getSex()+" "
                    ));
            studentService.mapStudentsBySex().get(Student.Sex.FEMALE).forEach(u-> System.out.println(u.getId()+" "
                            +u.getName()+" "
                            +u.getYear()+" "
                            +u.getSex()+" "
                    ));
        } catch (Exception e) {
            ///e.printStackTrace();
            System.out.println("有个空了");
        }
        ///5.删除指定学号的学生，返回是否成功删除
        System.out.println("----------------5.删除指定学号的学生，返回是否成功删除--------------------");

        System.out.println(studentService.removeStudent(201002));
        ((StudentServiceImpl) studentService).studentList.forEach(u-> System.out.println(u.getId()+" "
                +u.getName()+" "
                +u.getYear()+" "
                +u.getSex()+" "
        ));


    }
}

StudentServiceImpl

bash
package com.experiment04.service.impl;

import com.experiment04.entity.Student;
import com.experiment04.resource.DatabaseUtils;
import com.experiment04.service.StudentService;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class StudentServiceImpl implements StudentService {
public ListstudentList=new ArrayList();
我多加了个初始值方便测
public void util() {
///qingkong
studentList.removeIf(u->{
return true;
});
studentList.add(new Student(201001, Student.Sex.FEMALE, “赵阳阳”, 2010));

    studentList.add(new Student(201002, Student.Sex.MALE, "邵鹏", 2010));

    studentList.add(new Student(201103, Student.Sex.MALE, "高学斌", 2011));

    studentList.add(new Student(201104, Student.Sex.MALE, "张扬", 2011));

    studentList.add(new Student(201205, Student.Sex.FEMALE, "吕惠玲", 2012));

    studentList.add(new Student(201206, Student.Sex.MALE, "曾志优", 2012));
}
@Override
public List<Student> addStudent(Student student) {
    studentList.add(student);
    return studentList;
}

@Override
public List<Student> listStudentsByYear(int year) {
    List<Student>studentsYear=new ArrayList<Student>();
    /*studentList.forEach(u->{
        if(u.getYear()==year)
        {
            studentsYear.add(u);
        }
    });*/
    Stream<Student>stream =DatabaseUtils.getStudents().stream();
    Stream<Student>newstream= stream.filter(s->{
       if(s.getYear()==year){
           return true;
       }
       return false;
    });
    studentsYear=newstream.collect(Collectors.toList());
    return studentsYear;
}

@Override
public List<String> listStudentsNames(int year, Student.Sex sex) {
    List <String>yearSearchList=new ArrayList<String>();
    studentList.forEach(u->{
        if(u.getYear()==year && u.getSex()==sex)
        {
            yearSearchList.add(u.getName());
        }
    });
    return yearSearchList;

}

@Override
public Map<Student.Sex, List<Student>> mapStudentsBySex() {
    Map<Student.Sex,List<Student>> map=new HashMap<>();
    map.put(Student.Sex.MALE,new ArrayList<Student>());
    map.put(Student.Sex.FEMALE,new ArrayList<Student>());
    studentList.forEach(u->{
        if(u.getSex()== Student.Sex.MALE){
            map.get(Student.Sex.MALE).add(u);
        }
        if(u.getSex()== Student.Sex.FEMALE){
            map.get(Student.Sex.FEMALE).add(u);
        }
    });

    return map;
}

@Override
public boolean removeStudent(int id) {

//AtomicBoolean flag= new AtomicBoolean(false);
/* studentList=studentList.stream().filter(i->{
if(i.getId()!=id){

            return true;
        }
        return false;
    }).collect(Collectors.toList());
    return true;
    *//*return  studentList.removeIf(u->{
        if(u.getId()==id)
        {

            return true;
        }
        return false;
    });*//*

*/return DatabaseUtils.getStudents().removeIf(s->s.getId()==id);

}

#### DatabaseUtils
```bash```
package com.experiment04.resource;



import com.experiment04.entity.Student;



import java.util.ArrayList;

import java.util.List;



public class DatabaseUtils {

    private static final List<Student> STUDENTS = create();

    private static List<Student> create() {

        List<Student> students = new ArrayList<>();

        students.add(new Student(201001, Student.Sex.FEMALE, "赵阳阳", 2010));

        students.add(new Student(201002, Student.Sex.MALE, "邵鹏", 2010));

        students.add(new Student(201103, Student.Sex.MALE, "高学斌", 2011));

        students.add(new Student(201104, Student.Sex.MALE, "张扬", 2011));

        students.add(new Student(201205, Student.Sex.FEMALE, "吕惠玲", 2012));

        students.add(new Student(201206, Student.Sex.MALE, "曾志优", 2012));

        return students;

    }

    public static List<Student> getStudents() {

        return STUDENTS;

    }

}

StudentService

bash

package com.experiment04.service;
import com.experiment04.entity.Student;
import com.experiment04.resource.DatabaseUtils;

import java.util.List;
import java.util.Map;

public interface StudentService {

/**

 * 向集合添加一个学生，返回当前全部学生

 * @param student

 * @return

 */


List<Student> addStudent(Student student);



/**

 * 返回指定届的全部学生

 * @param year

 * @return

 */

List<Student> listStudentsByYear(int year);



/**

 * 返回指定届，指定性别的全部学生的姓名

 * @param year

 * @param sex

 * @return

 */

List<String> listStudentsNames(int year, Student.Sex sex);



/**

 * 将所有学生，以性别分组

 * @return

 */

Map<Student.Sex, List<Student>> mapStudentsBySex();



/**

 * 删除指定学号的学生，返回是否成功删除

 * @param id

 * @return

 */

boolean removeStudent(int id);

}

#### Student

```bash```
package com.experiment04.entity;
public class Student {
    public enum Sex {

        MALE, FEMALE
    }
    private int id;

    private Sex sex;

    private String name;

    // 例如2017级

    private int year;

    public Student(int id, Sex sex, String name, int year) {

        this.id = id;

        this.sex = sex;

        this.name = name;

        this.year = year;

    }
    下面全是set get
    public int getId() {

        return id;

    }



    public void setId(int id) {

        this.id = id;

    }



    public Sex getSex() {

        return sex;

    }



    public void setSex(Sex sex) {

        this.sex = sex;

    }



    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;

    }

}