把 Ex6-4 InnerClassTest.java 改成了這個樣子.

 

//----------------------------------------------------
//poor vertion
//use BankAccount to implement interface ActionListener
//----------------------------------------------------
import java.awt.event.*;
import java.text.*;
import javax.swing.*;

public class InnerClassTest2
{
   public static void main(String[] args)
   {
      BankAccount account=new BankAccount(10000);
      account.start(10);
      JOptionPane.showMessageDialog(null,"Quit program?");
      System.exit(0);
   }
}

class BankAccount implements ActionListener
{
   public BankAccount(double initialBalance)
   {
      balance=initialBalance;   
   }
   
   //private consturctor
   private BankAccount(double initialBalance,double initialRate)
   {
      balance=initialBalance;
      rate=initialRate;
   }
   
   public void start(double rate)
   {
      this.rate=rate;
      ActionListener adder=new BankAccount(this.balance,this.rate);   //inner class InterestAdder
      Timer t=new Timer(1000,adder);
      t.start();
   }
   
   private double balance;
   private double rate;
   

     
   public void actionPerformed(ActionEvent event)
   {
     double interest=balance*rate/100;
     balance+=interest;

     NumberFormat formatter=NumberFormat.getCurrencyInstance();
     System.out.println("balance="+formatter.format(balance));
   }   
}

 

效果上完全相同,但沒有可讀性