import java.util.Scanner;

public class test {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		while (in.hasNextInt()) {
			int num = in.nextInt();
			int count = 0;
			for (int i = 1; i <= num; i++) {
				// 默认是素数
				boolean flag = true;
				for (int j = 2; j <= Math.sqrt(i); j++) {
					if (i % j == 0) {
						// 能整除
						flag = false;
					}
				}
				if (flag) {
					count += 1;
					System.out.print(i + ",");
				}
			}
			System.out.print("在"+num+"以内的数中共计有" + count + "个素数");
		}

	}
}

执行结果如下：

100
1,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,在100以内的数中共计有26个素数