Question

我正在尝试编写一个接收用户指定号码的应用程序，然后制作那么多对象（我称之为学生）为他们分配一个随机名称和号码然后对他们的号码进行排序。我有各种各样的解决方案但是在打印数组时遇到了问题。我的代码如下。我得到的输出是“New Object”我输入的次数，然后是每个toString调用的“0：null”。任何帮助将不胜感激。谢谢。

import java.util.Random;
import java.util.Scanner;

public class application {

public static void main(String[] args) {

    int studentSerialNumber;
    String studentName;

    System.out.println("Enter the number of students you would like to sort: ");
    Scanner scanner = new Scanner(System.in);
    int numOfStudents = scanner.nextInt();

    Student[] anArrayToSort = new Student[numOfStudents];

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

        studentSerialNumber = ((int)(Math.random() * 8888)) + 1000;
        studentName = getStudentName();

        anArrayToSort[i] = new Student(studentSerialNumber, studentName);

    }

    for (int i = 0; i < anArrayToSort.length; i++) {
        System.out.println(anArrayToSort[i].toString());

    }
}

private static String getStudentName() {

    String studentName = "";
    int i = 7;
    Random r = new Random();

    while (i > 0) {
        char c = (char) (r.nextInt(26) + 'a');
        studentName = studentName + c;
        i--;
    }

    return studentName;
}
}


public class Student {

int studentSerialNumber;
String studentName;

Student(int studentSerialNumber, String studentName) {

    studentSerialNumber = studentSerialNumber;
    studentName = studentName;
    System.out.println("New Object");

}

public String toString() {
      return studentSerialNumber + ": " + studentName;
   }
}

Answer 1

构造函数中的赋值很糟糕：

Student(int studentSerialNumber, String studentName) {
    studentSerialNumber = studentSerialNumber;
    studentName = studentName;
    System.out.println("New Object");
}

这应该是：

Student(int studentSerialNumber, String studentName) {
    this.studentSerialNumber = studentSerialNumber;
    this.studentName = studentName;
    System.out.println("New Object");
}

目前，您要为自己分配值，而不是Student实例字段。

无法打印我的对象数组

1 个答案: