JAVA 基础编程练习题45 【程序 45 被 9 整除】

package cskaoyan;

public class cskaoyan45 {

	public static void main(String[] args) {

		// TODO Auto-generated method stub

		java.util.Scanner in = new java.util.Scanner(System.in);

		long prime = 0;

		long count = 1;

		long ret = 0;

		long i = 9;

		while (!isPrime(prime)) {

			System.out.println("请输入一个素数:");

			prime = in.nextLong();

		}

		while (i % prime != 0) {

			i = i * 10 + 9;

			count++;

		}

		ret = i;

		System.out.println("素数" + prime + "能整除" + count + "个9组成的数" + ret);

		in.close();

	}

	private static boolean isPrime(long number) {

		boolean flag = true;

		if (number < 2) {

			flag = false;

		} else if (number < 4) {

			flag = true;

		} else if (number % 2 == 0) {

			flag = false;

		} else {

			for (long i = 3; i < Math.sqrt(number) + 1; i++) {

				if (number % i == 0) {

					flag = false;

					break;

				}

			}

		}

		return flag;

	}

}