JAVA 基础编程练习题45 【程序 45 被 9 整除】

45 【程序 45 被 9 整除】

题目：判断一个素数能被几个 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;
}
}