判断是否为素数
package ch15;?
public class Prime {?
??? //主方法?
??? public static void main(String[] args) {?
??? //遍历1到100?
??? for (int i = 1; i < 100; i++) {?
??????? if (isPrime(i)) {?? //判断是否为素数?
??????? System.out.println(i);? //打印素数?
??????? }?
????? }?
??? }?
??? //判断一个整数是不是素数的方法?
??? private static boolean isPrime(int num) {?
????? if(num == 1)??? //1不是素数，直接返回false?
????? return false;?
????? //从2开始到该整数的2次根之间遍历?
????? long sprtNum = (long) Math.sqrt(num);?? //得到该数字的2次根?
????? for (int i = 2; i <= sprtNum; i++) {?
????????? if (num % i == 0) { //判断是否能除尽?
????????? return false;?? //返回false?
????????? }?
??????? }?
????? return true;??? //返回true?
????? }?
}
