用Java判断素数

import java.util.*;
public class panduansushu {
public static void main(String[] args) {
int x;
System.out.println("请输入一个正整数: ");
Scanner in=new Scanner(System.in);
x = in.nextInt();
if(judge(x)) {
System.out.println("它是素数.");
} else {
System.out.println("它不是素数.");
}
}
public static boolean judge(int y) {
int i,n = (int)Math.sqrt(y);
for(i=2;i<=n;i++)
{
if(y%i==0)
return false;
}
return true;
}
}