第十三行：怎么让Student类型的数组stu1调用下面的Student方法

Question

package zyntm;
import java.util.ArrayList;
import java.util.Scanner;
public class Users {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        ArrayList<String> stu = new ArrayList<String>();
        ArrayList<Student> stu1 = new ArrayList<Student>();
        int i = 0;
        while(true){
            String stuID = sc.next();
            stu.add(stuID);
            stu1.get(i) = new Student(stuID.substring(0, 4),stuID.substring(4, 6),stuID.substring(6, 8),stuID.substring(8, 10));
            i++;
        }
        class Student {
            String year;
            String spe;
            String class1;
            String num;
            Student(String year,String spe,String class1,String num){
                this.year = year;
                this.spe = spe;
                this.class1 = class1;
                this.num = num;
            }
            public String getYear() {
                return year;
            }
            public String getSpe() {
                return spe;
            }
            public String getClass1() {
                return class1;
            }
            public String getNum() {
                return num;
            }
        }
       }
}

第十三行：怎么让Student类型的数组stu1调用下面的Student方法？

Answer 1

改为stu1.add()方法， 然后把类Student放到Users类外即可，因为如果Student类放到Users类内，则创建Students类对象之前，需要先创建其外部类Users对象。

修改如下：

参考链接：

https://blog.csdn.net/kekekeliang/article/details/126760747

package zyntm;
import java.util.ArrayList;
import java.util.Scanner;
public class Users {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        ArrayList<String> stu = new ArrayList<String>();
        ArrayList<Student> stu1 = new ArrayList<Student>();
        int i = 0;
        while(true){
            String stuID = sc.next();
            stu.add(stuID);
            // 使用Arrrays类的add方法，将创建的每个学生类对象添加到stu1中
            stu1.add(new Student(stuID.substring(0, 4),stuID.substring(4, 6),stuID.substring(6, 8),stuID.substring(8, 10)));
          // 打印根据输入信息创建的学生的相关信息
            System.out.println("输入的信息为："+stu1.get(i));
            i++;
            
        }
        
        
        
    }
     
}
    
// 把学生类Student放到类Users类外
    class Student {
        String year;
        String spe;
        String class1;
        String num;
        Student(String year,String spe,String class1,String num){
            this.year = year;
            this.spe = spe;
            this.class1 = class1;
            this.num = num;
        }
        public String getYear() {
            return year;
        }
        public String getSpe() {
            return spe;
        }
        public String getClass1() {
            return class1;
        }
        public String getNum() {
            return num;
        }
        @Override
// 用于打印学生类的相关信息
        public String toString() {
            return "学生信息： [year=" + year + ", spe=" + spe + ", class1=" + class1 + ", num=" + num + "]";
        }
        
        
    }