public class HelloWorld{
? public static void main(String[] args){
??? int num = 999;
??? int count = 0;
??? while(num>=0 && num<=999999999){//為什么num>=0不正確，而num>0是正確的
??????? num = num/10;
??????? count++;
??? }
??? System.out.println("它是個"+count+"位的數！");
? }
}