innerclasstest.java

适合处学者JAVA者的代码

/**
   @version 1.00 2000-04-13
   @author Cay Horstmann
*/

import java.awt.event.*;
import java.text.*;
import javax.swing.*;

public class InnerClassTest
{  
   public static void main(String[] args)
   {  
      // construct a bank account with initial balance of $10,000
      BankAccount account = new BankAccount(10000);
      // start accumulating interest at 10%
      account.start(10);

      // keep program running until user selects "Ok"
      JOptionPane.showMessageDialog(null, "Quit program?");
      System.exit(0);
   }
}

class BankAccount
{  
   /**
      Constructs a bank account with an initial balance
      @param initialBalance the initial balance
   */
   public BankAccount(double initialBalance)
   {  
      balance = initialBalance;
   }

   /**
      Starts a simulation in which interest is added once per
      second
      @param rate the interest rate in percent
   */
   public void start(double rate)
   {
      ActionListener adder = new InterestAdder(rate);
      Timer t = new Timer(1000, adder);
      t.start();
   }

   private double balance;

   /**
      This class adds the interest to the bank account. 
      The actionPerformed method is called by the timer.
   */
   private class InterestAdder implements ActionListener
   {  
      public InterestAdder(double aRate)
      {
         rate = aRate;
      }

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

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

      private double rate;
   }
}