java实验四 集合与函数式编程实验

（2020.4.28版）
desktop/javacode/javatesthomework4

5.12版 改了StudentServiceImpl 为stream方式
5.19 优化removeif

nefu2020.4.28版，刚刚交

• • main
  • StudentServiceImpl
  • DatabaseUtils
  • StudentService
  • Student

1. 掌握集合的基本操作方法
2. 掌握Lambda表达式的声明编写规范
3. 掌握基于集合Stream的过滤/映射/聚合等操作
4. 掌握基于函数式编程集合元素的移除方法
   二、实验内容：
   初始化
   理解实验的目的，不要浪费时间在初始化的代码，直接复制使用

在com.experiment04.entity下，创建Student类，直接从github复制使用实验代码
在com.experiment04.resource下，创建DatabaseUtils类，直接从github复制使用实验代码，模拟添加若干对象
在com.experiment04.service下，创建StudentService接口，直接从github复制使用实验代码

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

在com.experiment04下，创建Test类，
为每个接口方法创建静态测试方法，在main()主函数调用
面向接口编程，测试StudentService接口中方法的实现

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();///方便看StudentServiceImpl studentServiceShow= (StudentServiceImpl) studentService;1.加入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));/1showstudentServiceShow.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

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 List<Student>studentList=new ArrayList<Student>();我多加了个初始值方便测public void util() {///qingkongstudentList.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));}@Overridepublic List<Student> addStudent(Student student) {studentList.add(student);return studentList;}@Overridepublic 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;}@Overridepublic 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;}@Overridepublic 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;}@Overridepublic 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

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

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

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 getpublic 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;}}

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