什么是质数？请求解答

public class Test {
public static void main(String[] args) {

boolean flag;

for (int i = 2; i <= 100; i++) {
flag = true;
for (int j = 2; j <= Math.sqrt(i); j++) {
if (i % j == 0) {
flag = false;
break;
}
}

if (flag) {
System.out.print(i + "\t");
}
}
}
}
你必须要== Math.sqrt()