```java
import java.util.ArrayList;
import java.util.Scanner;
public class shiyan2 {
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
int n=sc.nextInt();
shiyan2 Xll=new shiyan2();
shiyan21 s1=new shiyan21("god","dateStructure",100,"000");
shiyan21 s2=new shiyan21("Tom","Chinese",120,"001");
shiyan21 s3=new shiyan21("Jerry","dateStructure",20,"002");
shiyan21 s4=new shiyan21("Xll","dateStructure",233,"003");
shiyan21 s5=new shiyan21("lipu","dateStructure",11,"004");
System.out.println("1,显示全部记录");
System.out.println("2，输入添加学生信息");
System.out.println("3，删除学生信息（输入学号即可）");
System.out.println("4，学号排序");
System.out.println("5，课程排序");
System.out.println("0，退出程序");
boolean which=true;
while(true) {
switch(n) {
case 1: //我想把这个搞成第二class的show方法
ArrayList<shiyan21> Xinxi =new ArrayList<>();
if(Xinxi.size()!=0) {
Xinxi.add(s1);
Xinxi.add(s2);
Xinxi.add(s3);
Xinxi.add(s4);
Xinxi.add(s5);
for (int i = 0; i < Xinxi.size(); i++) {
System.out.println(Xinxi.get(i));
}}else {
System.out.println("快来添加几个学生吧！");
}
break;
case 2:
System.out.println("请输入您的基本信息");
Xll.AddStu//这里出错。
break;
case 3:
break;
case 4:
break;
case 5:
break;
case 0:
System.out.println("感谢你使用咸鲁力的编程，系统即将退出");
break;
}
}
}
}
```//第二个class，如果是接口请指教代码
import java.util.ArrayList;
import java.util.Scanner;
public class shiyan21 {
/*public void show() {//用屏幕展示学生的记 无法用构造方法表示
ArrayList<shiyan21> Xinxi = new ArrayList<>();
for (int i = 0; i < shiyan21.s; i++) {
System.out.println(shiyan21);
}
}*/
public String Id;
public String Name;
public String learn;
public int grade;
public shiyan21(String Name,String learn,int grade,String Id) {
this.grade=grade;
this.Id=Id;
this.learn=learn;
this.Name=Name;
}
public void AddStu(ArrayList<shiyan21> ayy) {
Scanner sc=new Scanner(System.in);
System.out.println("请输入你的姓名");
String name=sc.nextLine();
System.out.println("请输入你的课程");
String learn=sc.nextLine();
System.out.println("请输入你的成绩");
int grade=sc.nextInt();
System.out.println("请输入你的姓名");
String Id=sc.nextLine();
shiyan21 t=new shiyan21(Name, learn, grade, Id);
t.setGrade(grade);
t.setLearn(learn);
t.setName(name);
t.setId(Id);
}
public String getId() {
return Id;
}
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
public String getLearn() {
return learn;
}
public void setLearn(String learn) {
this.learn = learn;
}
public void setId(String Id) {
this.Id = Id;
}
public int getGrade() {
return grade;
}
public void setGrade(int grade) {
this.grade = grade;
}
public String DelStu(String whichid) {
return whichid;
}
public void SortByNo() {
}
public void SortByCourse() {
}
}
AddStu方法是shiyan21类中的。
shiyan2 Xll=new shiyan2();
你用shiyan2类的对象调用AddStu方法，这个类中并没有。
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