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/*我需要将一些信息存储在一个参差不齐的二维数组中。所以我希望这个程序能够接受 ex。3个名字，对于每个名字，我希望数组为每个名字存储一些课程。前任。名字安德斯参加了 3 门课程，oop、intP、appDesign。

我试图让它用 2 个 for 循环将此信息处理到数组中，但是循环有问题。希望任何人都可以帮助或给我一个线索。问候

package assignment10;

import java.util.Scanner;

public class NewClass {

    public static void main(String[] args) {

        System.out.println("Enter the number of students you want to enter into the database");

        Scanner number = new Scanner(System.in);

        int numberStudents = number.nextInt();

        int[] numberOfStudents = new int[numberStudents];

        for (int i = 0; i < numberOfStudents.length; i++) {

            numberOfStudents[i] = i+1; // here i avoid the length 0

        }
            System.out.println("you have entered " + numberStudents + " number of students");
        for (int j = 0; j < numberOfStudents.length; j++) {
            System.out.println(numberOfStudents[j]);
        }

        // This is here im having trouble Where in the for loops have i made the //mistake
        String [][] nameCourseArray =new String [numberOfStudents.length][];
        Scanner name = new Scanner(System.in);
        Scanner courseName = new Scanner ( System.in);
        for( int i = 0 ; i < numberOfStudents.length; i++ ){ // maybe here
            System.out.println("enter name of student");
            nameCourseArray[0][0] = name.nextLine();
            for( int j = 0;j < nameCourseArray[0].length; j++){ // or here
                System.out.println("Enter the courseName");
                nameCourseArray [i][j] =courseName.nextLine();


            }        


    }

}
}
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1 回答 1

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您只需初始化数组的第一个维度：

String [][] nameCourseArray =new String [numberOfStudents.length][];

这意味着nameCourseArray[i]为空，因此nameCourseArray[0][0]会nameCourseArray[i][j]抛出 NullPointerException。

您必须初始化第 i 个子数组：

nameCourseArray[i] = new String[someLength];
于 2015-04-17T11:57:46.003 回答