public class helloworld {
public static void main(String[] args){
int num = 999;
int count = 0;
if (num >= 0 && num<=999999999){
while(num != 0){
count++;
num/=10;// a/=b等同于a=a/b
}
System.out.println("他是个"+count+"位的数！");
}else{
System.out.println("输入有误！");
}
}
}
count是位数。count++是count=count+1。当num不等于0时，count至少是1.所以先执行count++，然后再判断num是否是高位数。
count++ --> 即count自加，相当于：count=count+1；
count++是count加1，代码类似于count=count+1;