Map映射

   1、创建一个学生类，包含以下属性：
         （1）学号stuNo,  姓名name,  分数score
         （2）进行合理的封装
    2、创建5个学生对象，各属性如下
    3、使用Map集合存放学生对象，集合中不能出现相同学号的学生信息（注：学生对象作为Map的value值）。
    4、对集合中的数据，做如下操作：
         （1）分数高于68的学生，加5分
         （2）计算平均分并输出
         （3）调整后的集合数据输出到控制台，（输出效果见下图，其中低于70为不及格）
         （4）将低于70分的学生从集合中删除
         （5）遍历输出删除后的集合*/

  参考如下：

Student.java 文件

package com.xiongluoluo.demo4;

public class Student {
    private String stuNo;
    private String name;
    private double score;

    public Student(){}

    public Student(String stuNo, String name, double score) {
        this.stuNo = stuNo;
        this.name = name;
        this.score = score;
    }

    @Override
    public String toString() {
        return "Student{" +
                "stuNo='" + stuNo + '\'' +
                ", name='" + name + '\'' +
                ", score=" + score +
                '}';
    }

    public String getStuNo() {
        return stuNo;
    }

    public void setStuNo(String stuNo) {
        this.stuNo = stuNo;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getScore() {
        return score;
    }

    public void setScore(double score) {
        this.score = score;
    }
}

　　

StudentTest.java  测试文件

package com.xiongluoluo.demo4;

import org.junit.jupiter.api.Test;

import java.util.*;

public class StudentTest {

    @Test
    public void test4(){
        Student student1 = new Student("001","dadada",93);
        Student student2 = new Student("002","dadada",88);
        Student student3 = new Student("003","dadada",33);
        Student student4 = new Student("004","dadada",66);
        Student student5 = new Student("005","dadada",55);

        Map<String,Student> map = new HashMap<>();
        map.put(student1.getStuNo(),student1);
        map.put(student2.getStuNo(),student2);
        map.put(student3.getStuNo(),student3);
        map.put(student4.getStuNo(),student4);
        map.put(student5.getStuNo(),student5);

        Set<Map.Entry<String, Student>> entrySet = map.entrySet();
        System.out.println("*****分数高于68的学生加5分*****");
        for(Map.Entry<String,Student> entry : entrySet){
            Student s = entry.getValue();
            if(s.getScore()>68){
                s.setScore(s.getScore()+5);
            }
            //System.out.println(s);
        }
        System.out.println("*****计算平均分并输出*****");
        double sum = 0;
        for(Map.Entry<String,Student> entry : entrySet){
            Student s = entry.getValue();
            sum += s.getScore();
            //System.out.println(s);
        }
        double avg = sum / map.size();
        System.out.println("平均分为:"+avg);
        System.out.println("*****调整后的集合数据输出到控制台，（输出效果见下图，其中低于70为不及格）*****");

        List<String> list = new ArrayList<>();

        for(Map.Entry<String,Student> entry : entrySet){
            Student s = entry.getValue();
            if(s.getScore()<70){
                System.out.println(s+"\t"+"不及格");
                list.add(entry.getKey());
            }else {
                System.out.println(s);
            }
        }
        System.out.println("*****将低于70分的学生从集合中删除*****");
        for(String stuNo : list){
            map.remove(stuNo);
        }
        System.out.println("*****遍历输出删除后的集合*****");
        for(Map.Entry<String,Student> entry : entrySet){
            Student s = entry.getValue();
            System.out.println(s);
        }

    }
}