java一道存款题

class Account 
{
        String name;
  protected double balance;
 Account (String str,double amt)
                 {
           name=str;
              balance =amt;
                 }
   String getname()
           {
                return name;
            }
    double getbalance()
             {
                        return balance;
             }
     void in(double arm)
         {
           balance+=arm;
             System.out.println("存款:"+arm);
           }
    void  out (double arm)
              {
                     balance-=arm;
          System.out.println("取款:"+arm);
               }
}
class Saving   extends Account
{
              double interest;
   Saving(String str,double amt,double rate )
{
 super(str,amt);
interest=rate;
}}
class Checking   extends Account
{
           double  overdraft;
       Checking(String str,double amt)
         {
                 super(str,amt);
           }
       Checking (String str ,double amt,double raft)
            {
                           super(str,amt);
                            overdraft=raft;
            }
        void    out(double arm)
           {
              System.out.println("透支金额:"+overdraft);
             if(arm<=balance)
             {
                balance-=arm;
             System.out.println("取款:"+arm);
             }else if((arm>balance)&&(arm>(balance+overdraft)))
               { 
                   System.out.println("对不起！您不能取款！");
                  }else
                  {
                      double result=arm-balance; 
                             balance=0;
                 System.out.println("取款:"+arm);
                     System.out.println("当前透支金额:"+result);
                  }       
 }  
}
class Accounttest
{
          Accounttest()
         {
         }
  public static void main(String[] args) {        Saving saving = new Saving ("John", 500, 0.04);
        System.out.println("\n储蓄帐户详细信息");
        System.out.println("------------------------");
        System.out.println("" + saving.getname()
            + "初始余额为： " + saving.getbalance());
        saving.in(200);
        saving.out(200);
        System.out.println("" + saving.getname()
            + "交易后余额为： "
            + saving.getbalance());        System.out.println("\n支票帐户详细信息");
        System.out.println("------------------------");        Checking  checking = new  Checking("Stephen", 200, 200);
        System.out.println("" + checking.getname()
            + "初始余额为： " + checking.getbalance());
        checking.in(200);
        checking.out(500);
        System.out.println("" + checking.getname()
            + "交易后余额为： "
            + checking.getbalance());
    }}
如何改为存款和取款是执行的时候输入进去的，而不是在里定好的。