Question

此代码中有一个错误，我无法使用oop将数组列表分配给数组，也无法找到解决方法！我将我的代码和类放在这里，以便任何人都可以帮助我找出问题所在！！！

package java808session06app04classnumber03;

import java.util.ArrayList;
import java.util.Scanner;

public class Java808session06app04classnumber03 {


public static void main(String[] args) {


    final int SCHOOL_CLASS_NUMBER = 3;

    Scanner user = new Scanner(System.in);

    SchoolClass[] schoolClassArray = new SchoolClass[SCHOOL_CLASS_NUMBER];

    int intNextStudent = 1;
    int intAvg = 0;

    for (int i = 0; i < SCHOOL_CLASS_NUMBER; i++) {
        System.out.println("Class " + (i + 1) + ": ");

        do {
            ArrayList<Student> studentList = new ArrayList<>();
            Student st01 = new Student();
            System.out.print("Enter student name: ");
            st01._name = user.next();
            System.out.print("Enter student family: ");
            st01._family = user.next();
            System.out.print("Enter student grade01: ");
            st01._grade01 = user.nextInt();
            System.out.print("Enter student grade02: ");
            st01._grade02 = user.nextInt();
            System.out.print("Enter student grade03: ");
            st01._grade03 = user.nextInt();
            System.out.print("Enter student grade04: ");
            st01._grade04 = user.nextInt();

            studentList.add(st01);

            System.out.print("Is next student (1 for next student): ");
            intNextStudent = user.nextInt();


            schoolClassArray[i].studentList = studentList;
        } while (intNextStudent == 1);

    } 
  }
}

这些是我为这段代码制作的类！

班级School

{
ArrayList<Student> studentList = new ArrayList<>();
}

班级学生

{
String _name;
String _family;
int _grade01;
int _grade02;
int _grade03;
int _grade04;
 }

Answer 1

您忘了初始化数组中的SchoolClass。

紧接着

for (int i = 0; i < SCHOOL_CLASS_NUMBER; i++) {

插入一行：

schoolClassArray[i] = new SchoolClass();

Answer 2

我不确定您要使用提供的代码做什么。我发现您的代码中有1个潜在错误，在do循环的开始，您在每次迭代中都创建了一个新的ArrayList，因此应将其移出do循环。对于ArrayList至Array部分，您可以执行类似以下操作（Source）：

List<String> list = new ArrayList<String>();
list.add("India");
list.add("Switzerland");

String [] countries = list.toArray(new String[list.size()]);

如何使用oop将arraylist分配给数组？

2 个答案: