初学java,请指教一个问题

给你改了一下，呵呵 public  static  void  main(String  args[])
throws  IOException
{
boolean  choice;
choice=true;
String  num,quantity;
char[]  ch;
int  a,b;
double  total_price=0;
BufferedReader  br=new  BufferedReader(new  InputStreamReader(System.in));
System.out.println("商品代号                 商品名称                 单价(元)");
System.out.println("    1                 双飞燕光电鼠                 80");
System.out.println("    2                 步行者低音炮                 350");
System.out.println("    3                 长城电源                     150");
System.out.println("    4                 罗技无线光电鼠套装           280");
System.out.println("    5                 废柴                         1");
System.out.println("    6                 WindowsXP盗版光碟            4");
System.out.println("    7                 Cache                        0");
System.out.println("    8                 ……                         10000\n");
outer:
        while(choice)
{
System.out.print("请输入你需要购买的商品代号：");
num=br.readLine();
b=Integer.parseInt(num);
System.out.print("请输入你需要购买该商品的数量：");
quantity=br.readLine();
a=Integer.parseInt(quantity);
if((b>=1)&&(b<=8)&&(a>=0))
{
switch(b)
{
case  1:
total_price=total_price+80*a;
 break;
 case  2:
     total_price=total_price+350*a;
     break;
  case  3:
  total_price=total_price+150*a;
break;
  case  4:
  total_price=total_price+280*a;
  break;
  case  5:
  total_price=total_price+1*a;
  break;
  case  6:
  total_price=total_price+4*a;
  break;
  case  7:
  total_price=total_price+0*a;
  break;
  case  8:
  total_price=total_price+10000*a;
  break;
}
}
System.out.println("你目前所购买的物品的总价为："+total_price);
System.out.print("按Y/y继续购物，按N/n退出：");
ch = br.readLine().toCharArray();
switch(ch[0])
{
case  'Y':
case  'y':
continue outer;
case  'N':
case  'n':
choice=false;
    break;
}
}
}