杭电OJ2091，求答疑

杭电OJ2091 为什么输入@的时候，程序不结束呢？求大神解答
import java.util.Scanner;

public class No_2091 {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
while (s.hasNext()){
String str = s.next();
int n = s.nextInt();
if(str=="@"){
break;
}
for(int i =1;i<=n;i++){
for(int k=0;k<=n-i;k++){
System.out.print(" “);
}
for(int j =1;j<=2i-1;j++){
if(j == 1 || j == 2i-1 || i == n){
System.out.print(str);
}else{
System.out.print(” ");
}
}
System.out.println();
}
}
}
}