POJ3006 java

判断是否为素数，并计数

import java.util.Scanner;


public class Main {
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		
		while(true) {
			int a=sc.nextInt();
			int d=sc.nextInt();
			int n=sc.nextInt();
			if((a*a+d*d+n*n)==0) {
				break;
			}
			int count=0;
			for (int i = a; ; i+=d) {
				if(isPrime(i)) {
					count++;
				}
				if(count==n) {
					System.out.println(i);
					break;
				}
			}
		}
	}

	private static boolean isPrime(int i) {
		if(i==2 || i==3) {
			return true;
		}
		if(i%6!=5 && i%6!=1 ||i==1) {
			return false;
		}
		int sqrt=(int) Math.sqrt(i);
		for (int j = 5; j <= sqrt; j+=6) {
			if(i%j==0 ||i%(j+2)==0) {
				return false;
			}
		}
		return true;
	}
	
}