java - 如何在这个素数生成器中实现数字序列？

Question

我不确定如何创建可以放置在打印素数的每次迭代之前的数字序列。感谢您提供的任何帮助。

public class CountingPrimes {

public static void main(String[] args) {
    int flag = 0, i, j;
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter the 1st number: ");
    int firstNum = sc.nextInt();

    System.out.println("Enter the 2nd number: ");
    int secondNum = sc.nextInt();
    System.out.println("Counting prime numbers between "
            + firstNum + " and " + secondNum + ":");
    for (i = firstNum; i <= secondNum; i++) {
        for (j = 2; j < i; j++) {
            if (i % j == 0) {
                flag = 0;
                break;
            } else {
                flag = 1;
            }
        }
        if (flag == 1) {      
            System.out.println(i);
                }
        }


    }
}

现在，我的代码输出(在用户输入两个数字后):

Counting prime numbers between 1 and 14:
 3
 5
 7
 11
 13

我需要的代码如下:

Counting prime numbers between 1 and 14:
1. 3
2. 5
3. 7
4. 11
5. 13

此外，如果您能看到我可以更改的任何错误或改进，我将不胜感激。再次感谢您!

Answer 1

您可以使用计数器并在打印素数时打印计数器。每次增加计数器。

int counter = 1;
int flag = 0, i, j;
.....
if (flag == 1) {
    System.out.format("%d. %d\n", counter, i);
    counter++;
}