脑子都要想爆了。。智商好捉急啊。。问了一下百度得到了答案，一看就懂，又很简单，谁能指点一下关键步骤啊。。是不是不适合当程序员，呜呜
public static void main(String[] args) {
int num = 90;
int k = 2;
System.out.print(num + "=");
while (num > k) {
if (num % k == 0) {
System.out.print(k + "×");
num = num / k;
}
if (num % k != 0) {
k++;
}
}
System.out.println(k);
}