内部类实现机制

来源：互联网发布：dll不兼容windows 编辑：程序博客网时间：2024/04/28 18:20

package timer;

import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Date;

import javax.swing.JOptionPane;
import javax.swing.Timer;

/**
* 内部类，可以通过反射看出程序中实现的机制
*
* 1.不是每个TalkingClock都有一个TimePrinter实例域，TimePrinter对象是由TalkingClock类的方法构造的
* 2.在TalkingClock类中，编译器加了
*   static boolean access$0(TalkingClock);
*   将返回作为参数传递给它的对象域beep - 为内部类访问外部类，增加了特权 - 不安全
* 3.在TimePrinter类中，编译器加了
*   public timer.TalkingClock$TimePrinter(TalkingClock);
*   final timer.TalkingClock this$0;
*   用于引用外围类(TalkingClock)的对象
*/
public class InnerClassTest {
public static void main(String[] args) {
  TalkingClock clock = new TalkingClock(3000, true);
  clock.start();

  JOptionPane.showMessageDialog(null, "Quit program?");
  System.exit(0);
}
}

class TalkingClock {

private int interval;
private boolean beep;

public TalkingClock(int interval, boolean beep) {
  this.interval = interval;
  this.beep = beep;
}

public void start() {
  ActionListener listener = new TimePrinter();
  Timer timer = new Timer(interval, listener);
  timer.start();
}

public class TimePrinter implements ActionListener {

  @Override
  public void actionPerformed(ActionEvent event) {
   Date now = new Date();
   System.out.println("At the tone, the time is : " + now);
   /**
    * if(beep)
    * if(access$0(TalkingClock))
    * 等价
    */
   if(beep) {
    Toolkit.getDefaultToolkit().beep();
   }
  }

}
}