为什么要用内部类:掌握框架[Java编程]

//: Event.java
// The common methods for any control event
package c07.controller;

abstract public class Event {
  private long evtTime;
  public Event(long eventTime) {
    evtTime = eventTime;
  }
  public boolean ready() {
    return System.currentTimeMillis() >= evtTime;
  }
  abstract public void action();
  abstract public String description();
} ///:~

//: Controller.java
// Along with Event, the generic
// framework for all control systems:
package c07.controller;

// This is just a way to hold Event objects.
class EventSet {
  private Event[] events = new Event[100];
  private int index = 0;
  private int next = 0;
  public void add(Event e) {
    if(index >= events.length)
      return; // (In real life, throw exception)
    events[index++] = e;
  }
  public Event getNext() {
    boolean looped = false;
    int start = next;
    do {
      next = (next + 1) % events.length;
      // See if it has looped to the beginning:
      if(start == next) looped = true;
      // If it loops past start, the list 
      // is empty:
      if((next == (start + 1) % events.length)
         && looped)
        return null;
    } while(events[next] == null);
    return events[next];
  }
  public void removeCurrent() {
    events[next] = null;
  }
}

public class Controller {
  private EventSet es = new EventSet();
  public void addEvent(Event c) { es.add(c); }
  public void run() {
    Event e;
    while((e = es.getNext()) != null) {
      if(e.ready()) {
        e.action();
        System.out.println(e.description());
        es.removeCurrent();
      }
    }
  }
} ///:~

//: GreenhouseControls.java
// This produces a specific application of the
// control system, all in a single class. Inner
// classes allow you to encapsulate different
// functionality for each type of event.
package c07.controller;

public class GreenhouseControls 
    extends Controller {
  private boolean light = false;
  private boolean water = false;
  private String thermostat = "Day";
  private class LightOn extends Event {
    public LightOn(long eventTime) {
      super(eventTime);
    }
    public void action() {
      // Put hardware control code here to 
      // physically turn on the light.
      light = true;
    }
    public String description() {
      return "Light is on";
    }
  }
  private class LightOff extends Event {
    public LightOff(long eventTime) {
      super(eventTime);
    }
    public void action() {
      // Put hardware control code here to 
      // physically turn off the light.
      light = false;
    }
    public String description() {
      return "Light is off";
    }
  }
  private class WaterOn extends Event {
    public WaterOn(long eventTime) {
      super(eventTime);
    }
    public void action() {
      // Put hardware control code here
      water = true;
    }
    public String description() {
      return "Greenhouse water is on";
    }
  }
  private class WaterOff extends Event {
    public WaterOff(long eventTime) {
      super(eventTime);
    }
    public void action() {
      // Put hardware control code here
      water = false;
    }
    public String description() {
      return "Greenhouse water is off";
    }
  }
  private class ThermostatNight extends Event {
    public ThermostatNight(long eventTime) {
      super(eventTime);
    }
    public void action() {
      // Put hardware control code here
      thermostat = "Night";
    }
    public String description() {
      return "Thermostat on night setting";
    }
  }
  private class ThermostatDay extends Event {
    public ThermostatDay(long eventTime) {
      super(eventTime);
    }
    public void action() {
      // Put hardware control code here
      thermostat = "Day";
    }
    public String description() {
      return "Thermostat on day setting";
    }
  }
  // An example of an action() that inserts a 
  // new one of itself into the event list:
  private int rings;
  private class Bell extends Event {
    public Bell(long eventTime) {
      super(eventTime);
    }
    public void action() {
      // Ring bell every 2 seconds, rings times:
      System.out.println("Bing!");
      if(--rings > 0)
        addEvent(new Bell(
          System.currentTimeMillis() + 2000));
    }
    public String description() {
      return "Ring bell";
    }
  }
  private class Restart extends Event {
    public Restart(long eventTime) {
      super(eventTime);
    }
    public void action() {
      long tm = System.currentTimeMillis();
      // Instead of hard-wiring, you could parse
      // configuration information from a text
      // file here:
      rings = 5;
      addEvent(new ThermostatNight(tm));
      addEvent(new LightOn(tm + 1000));
      addEvent(new LightOff(tm + 2000));
      addEvent(new WaterOn(tm + 3000));
      addEvent(new WaterOff(tm + 8000));
      addEvent(new Bell(tm + 9000));
      addEvent(new ThermostatDay(tm + 10000));
      // Can even add a Restart object!
      addEvent(new Restart(tm + 20000));
    }
    public String description() {
      return "Restarting system";
    }
  }
  public static void main(String[] args) {
    GreenhouseControls gc = 
      new GreenhouseControls();
    long tm = System.currentTimeMillis();
    gc.addEvent(gc.new Restart(tm));
    gc.run();
  } 
} ///:~