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代码小白liu 发表于 2022-7-8 08:27:53

帮忙看看哪里错了

import java.io.Serializable;
import java.util.Objects;

public class Student implements Serializable {

private static final long serialVersionUID= 1L;
private int stuNo;
private Stringname;
private boolean sex;
private String email;
private String birthday;

public Student() {
}

public Student(int stuNo, String name, boolean sex, String email, String birthday) {
   this.stuNo = stuNo;
   this.name = name;
   this.sex = sex;
   this.email = email;
   this.birthday = birthday;
}

public String getEmail() {
   return email;
}

public void setEmail(String email) {
   this.email = email;
}

public String getBirthday() {
   return birthday;
}

public void setBirthday(String birthday) {
   this.birthday = birthday;
}

public Student(int stuNo, String name, boolean sex) {
   this.stuNo = stuNo;
   this.name = name;
   this.sex = sex;
}

public int getStuNo() {
   return stuNo;
}

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

public String getName() {
   return name;
}

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

public boolean isSex() {
   return sex;
}

public void setSex(boolean sex) {
   this.sex = sex;
}

@Override
public boolean equals(Object o) {
   if (this == o) return true;
   if (o == null || getClass() != o.getClass()) return false;
   Student student = (Student) o;
   return stuNo == student.stuNo &&
            sex == student.sex &&
            Objects.equals(name, student.name) &&
            Objects.equals(email, student.email) &&
            Objects.equals(birthday, student.birthday);
}

@Override
public int hashCode() {
   return Objects.hash(stuNo, name, sex, email, birthday);
}

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

}

import org.omg.PortableInterceptor.INACTIVE;

import java.io.*;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;

public class ShowStudentPage {
public void rukou(){
   while (true){
      /* 欢迎使用学生信息管理系统，请认真阅读以下使用说明：
         请输入不同的功能编号来选择不同的功能：
               查看学生列表
               保存学生
               删除学生
               查看某个学生详细信息*/
         System.out.println("欢迎使用学生信息管理系统，请认真阅读以下使用说明：+\n" +
               "请输入不同的功能编号来选择不同的功能："+"\n"+"" +
                        " 查看学生列表\n" +
                        " 保存学生\n" +
                        " 删除学生\n" +
                        " 查看某个学生详细信息");
         Scanner s = new Scanner(System.in);
         System.out.print("请输入功能编号：");
         int no = s.nextInt();
         if (no == 1){
            showStuInfo();
         }else if (no == 2){
            saveStudent();
         }else if(no == 3 ){
            deleteStu();
         }else if(no == 4){
            showStuAllInfo();

         }else{
            System.out.println("输入的编号有误，请重新输入！");
         }

   }
}

//保存学生
public void saveStudent() {
   Scanner s = new Scanner(System.in);
   Student student = new Student();

   System.out.println("请输入学生编号：");
   student.setStuNo(s.nextInt());

   System.out.println("请输入学生姓名：");
   student.setName(s.next());

   System.out.println("请输入学生性别：");
   student.setSex((s.next().equals("男")));

   System.out.println("请输入学生生日：");
   student.setBirthday(s.next());

   System.out.println("请输入学生邮箱：");
   student.setEmail(s.next());

   Map<Integer, Student> studentMap = readMap();
   studentMap.put(student.getStuNo(),student);
   saveMap(studentMap);
}

//展示学生列表
public void showStuInfo() {
   System.out.println("------------------------------");
   System.out.println("学生信息列表展示");
   System.out.println("------------------------------");
   System.out.println("学号\t姓名\t性别");

   Map<Integer,Student> map= readMap();
   Set<Map.Entry<Integer,Student>> set = map.entrySet();
   for (Map.Entry<Integer,Student> s : set) {
         System.out.println(s.getKey()+"\t" + s.getValue().getStuNo() + "\t" + s.getValue().getName() +
               (s.getValue().isSex()?"男" : "女"));
   }
}

//展示学生详细信息
public void showStuAllInfo(){
   Scanner s = new Scanner(System.in);
   System.out.print("请输入学生编号：");
   int no = s.nextInt();
   Map<Integer,Student> map= readMap();
   Set<Map.Entry<Integer,Student>> set = map.entrySet();
   for (Map.Entry<Integer,Student> s1 : set) {
         if (no==s1.getKey()){
            System.out.println("学号：" + s1.getKey()+ "\n" +"姓名：" +s1.getValue().getName() + "\n"+"生日：" +
                     s1.getValue().getBirthday() + "\n" + "性别："+
                           (s1.getValue().isSex()?"男" : "女") + "\n"+ "邮箱:" + s1.getValue().getEmail());
         }else{
            System.out.println("您输入的学生编号不存在，请重新输入！");

         }    }
}
//删除学生
public void deleteStu() {
   Scanner s3 = new Scanner(System.in);
   System.out.print("请输入要删除的学生编号：");
   int no = s3.nextInt();
   Map<Integer,Student> map = readMap();
   map.remove(no);
   saveMap(map);
}
//序列化学生集合
public void saveMap(Map<Integer,Student>map) {
   ObjectOutputStream oos = null;
   try {
         oos = new ObjectOutputStream(new FileOutputStream("StuInfo"));
         oos.writeObject(map);
         oos.flush();

   } catch (IOException e) {
         e.printStackTrace();
   } finally {
         if (oos != null) {
            try {
               oos.close();
            } catch (IOException e) {
               e.printStackTrace();
            }
         }
   }
}

//反序列化
public Map<Integer, Student> readMap() {
   ObjectInputStream ois = null;
   try {
         Map<Integer,Student> map = null;
         ois = new ObjectInputStream(new FileInputStream("StuInfo"));
      if (null != ois){
            map = (Map<Integer,Student>) ois.readObject();
      }

         return map;
   } catch (IOException e) {
         e.printStackTrace();

   } catch (ClassNotFoundException e) {
         e.printStackTrace();
   } finally {
         if (ois != null) {

            try {
               ois.close();
            } catch (IOException e) {
               e.printStackTrace();
            }
         }
   }
   return null;
}
}
public class Test {
public static void main(String[] args) {
   ShowStudentPage showStudentPage = new ShowStudentPage();
   showStudentPage.rukou();
}
}

最后运行报错

欢迎使用学生信息管理系统，请认真阅读以下使用说明：+
请输入不同的功能编号来选择不同的功能：
查看学生列表
保存学生
删除学生
查看某个学生详细信息
请输入功能编号：1
------------------------------
学生信息列表展示
------------------------------
学号姓名性别
java.io.EOFException
at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2335)
at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:2804)
at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:802)
at java.io.ObjectInputStream.<init>(ObjectInputStream.java:299)
at ShowStudentPage.readMap(ShowStudentPage.java:139)
at ShowStudentPage.showStuInfo(ShowStudentPage.java:78)
at ShowStudentPage.rukou(ShowStudentPage.java:28)
at Test.main(Test.java:4)
Exception in thread "main" java.lang.NullPointerException
at ShowStudentPage.showStuInfo(ShowStudentPage.java:79)
at ShowStudentPage.rukou(ShowStudentPage.java:28)
at Test.main(Test.java:4)

Process finished with exit code 1

豆嘉木 发表于 2022-7-8 08:48:50

看提示语“Exception in thread "main" java.lang.NullPointerException”，指针为空，是不是野指针(或者说悬空指针)

代码小白liu 发表于 2022-7-8 09:03:32

豆嘉木发表于 2022-7-8 08:48
看提示语“Exception in thread "main" java.lang.NullPointerException”，指针为空，是不是野指针(或者说 ...

找不出原因呀

风华叶冷 发表于 2022-8-1 09:43:21

同上，空指针异常，应该是readMap反序列化的地方出了问题，可以尝试在那边每隔一行输出一个1 23 4 5 6 这样排除是哪一行有问题，难道是路径问题

风华叶冷 发表于 2022-8-1 09:47:01

风华叶冷发表于 2022-8-1 09:43
同上，空指针异常，应该是readMap反序列化的地方出了问题，可以尝试在那边每隔一行输出一个1 23 4 5 6 这 ...

不确定，可以现在查询学生那里先检查一下是不是readMap出错了

不会起名字的我 发表于 2022-8-2 09:12:20

报错 EOF ，这个流根本没有被生成，而是直接结束了这个流，下面的空指针就是因为这个而出现的

不会起名字的我 发表于 2022-8-2 09:23:31

如果流里的数据是空的，用 ObjectInputStream 就会报 EOF ，不同于字节流，如果是空的就返回 -1

一颗yan 发表于 2023-1-6 15:31:35

showStuInfo() 方法里 Map<Integer,Student> map= readMap(); 加判空

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