public?class?HelloWorld{
public?static?void?main(String[]?args){
????int?num?=?999;
????int?count?=?0;
????for?(;num?>=?0??&&?num<=999999999;count++){
????????num=num/10;
????}
????System.out.println("它是個(gè)"+?count+"位的數(shù)！");
????}
}

【后來(lái)證明，可以運(yùn)行】