account.java

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    class AccountException extends Exception  //自定义帐户异常类
    {
      public AccountException() {super();}
      public AccountException(String s) {super(s);}
    }
    
    class NotEnoughBalanceException extends AccountException  //余额不足异常
    {
      Account account;
      
      public NotEnoughBalanceException(Account a)
      {
        super("余额不足！");
        account = a;
      }
      
      public String toString()
      {
        return "帐户["+account.toString()+"]的余额不足！";
      }
    }
    
    class OutOfLimitException extends AccountException       //取款超出范围
    {
      Account account;
      double maxLimit;
      
      public OutOfLimitException(Account a, double limit)
      {
        super("超出取款最大金额！");
        account = a;
        maxLimit = limit;
      }
      
      public String toString()
      {
        return "帐户["+account.toString()+"]每次最多取款["+maxLimit+"]元！";
      }
    }
    
    class Account  // 帐户类
    {
      private String ID;
      private double balance;
      // ...
      
      public Account(String aID, double b)
      {
        ID = aID;
        balance = b;
      }
      
      public void drawing(double m) throws AccountException  //取款方法
      {
        if(balance<m)    // 检测错误
        {
          if(m>1000.00)  // 检测错误
            throw new OutOfLimitException(this,1000.00);  //抛出异常
          else
            throw new NotEnoughBalanceException(this);    //抛出异常
        }
        else
          balance = balance - m;
      }
      
      public double getBalance()
      {
        return balance;
      }
      
      public String toString()
      {
        return ID;
      }
      
      // ...
    }
    
    class AccountTest
    {
      public static void main(String[] args) throws Exception
      {
        Account acc = new Account("10001",200.0);
        
        if(args.length==1)
        {
          try
          {
            System.out.println("取款前余额："+acc.getBalance());
            acc.drawing(Double.parseDouble(args[0]));  // 可能抛出异常
            System.out.println("取款后余额："+acc.getBalance());
          }
          catch(NotEnoughBalanceException e)
          {
            System.err.println(e);
          }
          catch(OutOfLimitException e)
          {
            System.err.println(e);
          }
          catch(AccountException e)
          {
            System.err.println("其它的帐号异常！");
          }
          catch(Exception e)
          {
            System.err.println("其它的异常！\n"+e);
            throw e;
          }
        }
        else
        {
          System.out.println("指定一个数值作为命令行参数！");
        }
      }
    }