Question

我正在使用Java制作预订系统，我想创建随机ID号。（我要显示的代码不是我班级中的所有代码，只是与之相关的内容。）

我已经命名了一个字段randomGenerator，它是一个Random对象并在我的构造函数中声明它：

public class ReservationSystem {
     private Random randomGenerator;

     public ReservationSystem() {
           randomGenerator = new Random();
     }

然后这是我遇到困难的方法：

     public void generateCustomerID(String id, int numbersInID) {
     //incNumber stands for incremented number
     int incNumber = 1;
     //create a new array of numbers as big as the user has defined
     int[] numbers = new int[numbersInID];
     while(numbersInID < (incNumber +1)) {
         //add a new number to the array between 0 and 10
         numbers[incNumber] = randomGenerator.nextInt(10);
         incNumber++;
     }
     System.out.print(id);
     for(int number: numbers)
         System.out.print(number);
 }

在我的申请中，我已经给出了这些价值观：

  public class Application { 
       public static void main(String[] args) {
               reserve.generateCustomerID("AB-", 3);
        }
  }

我一直在收到输出 AB-000 。

Answer 1

数组的索引从Java开始，而不是1。
条件numbersInID < (incNumber +1)错误，当numbersInID为3时，循环体不会被执行。

试试这个：

public void generateCustomerID(String id, int numbersInID) {
    //incNumber stands for incremented number
    int incNumber = 0;
    //create a new array of numbers as big as the user has defined
    int[] numbers = new int[numbersInID];
    while(incNumber < numbersInID) {
        //add a new number to the array between 0 and 10
        numbers[incNumber] = randomGenerator.nextInt(10);
        incNumber++;
    }
    System.out.print(id);
    for(int number: numbers)
        System.out.print(number);
}

Answer 2

问题在于：

while(numbersInID < (incNumber +1)) { // ← *here*
     //add a new number to the array between 0 and 10
     numbers[incNumber] = randomGenerator.nextInt(10);
     incNumber++;
 }

应该是numbersInID 更大而不是incNumber：

int incNumber = 0;
while(numbersInID > incNumber) {
     //add a new number to the array between 0 and 10
     numbers[incNumber] = randomGenerator.nextInt(10);
     incNumber++;
 }

Java中的随机类

2 个答案: