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“迭代器”设计模式： 内部类实现了迭代接口，按它们自己的方式实现这个接口（每个迭代器按照自己的方法迭代外部类对象包含的元素，例中外部类包装了一个数组） 同一个外部类可以用多个内部类同时实现该接口，但具体实现不同，就拥有了不同的迭代功能 别的方法能以此接口为参数，来生成更加通用的代码（利用多态） interface Selector { boolean end(); Object current(); void next(); } public class Sequence { private Object[] items; private int next = 0; public Sequence(int size) { items = new Object[size]; } public void add(Object x) { if (next < items.length) items[next++] = x; } private class SequenceSelector implements Selector { private int i = 0; public boolean end() { return i == items.length; } public Object current() { return items; } public void next() { if (i < items.length) i++; } } public Selector selector() { return new SequenceSelector(); } public static void main(String[] args) { Sequence sequence = new Sequence(10); for (int i = 0; i < 10; i++) sequence.add(Integer.toString(i)); Selector selector = sequence.selector(); while (!selector.end()) { System.out.print(selector.current() + " "); selector.next(); } } } /* * Output: 0 1 2 3 4 5 6 7 8 9 */// :~ 使用匿名内部类的工厂方法设计模式 没有单独创建工厂类 工厂被写为Service实现中的一个static域（字段），使用匿名内部类，实现了接口的getService方法 Service实现类的构造方法设为私有，Service对象只能通过工厂字段的getSerice()获得 import static net.mindview.util.Print.*; interface Service { void method1(); void method2(); } interface ServiceFactory { Service getService(); } class Implementation1 implements Service { private Implementation1() {} public void method1() {print("Implementation1 method1");} public void method2() {print("Implementation1 method2");} //工厂在这 public static ServiceFactory factory = new ServiceFactory() { public Service getService() { return new Implementation1(); } }; } class Implementation2 implements Service { private Implementation2() {} public void method1() {print("Implementation2 method1");} public void method2() {print("Implementation2 method2");} //还有这 public static ServiceFactory factory = new ServiceFactory() { public Service getService() { return new Implementation2(); } }; } public class Factories { public static void serviceConsumer(ServiceFactory fact) { Service s = fact.getService(); s.method1(); s.method2(); } public static void main(String[] args) { serviceConsumer(Implementation1.factory); // Implementations are completely interchangeable: serviceConsumer(Implementation2.factory); } } /* Output: Implementation1 method1 Implementation1 method2 Implementation2 method1 Implementation2 method2 *///:~ 模板方法设计模式 模板方法包含算法的基本结构，并且会调用一个或者多个可覆盖的方法 （骨架是确定的，细节是可扩展的） （设计模式总是将变化的事物与保持不变的事物分离开，这里模板方法是不变的，可覆盖方法是变化的） 模板方法的应用： 应用程序框架（application framework），是被设计用来解决某类特定问题的一个类或一组类 要应用某个应用程序框架，通常是继承这个（组）类并重写方法，以解决特定问题 控制框架（control framework）是一类特殊的应用程序框架，需求是响应事件 主要用来响应事件的系统被称作事件驱动系统（GUI几乎完全是事件驱动的系统，java Swing库就是一个控制框架） 关键词：控制 事件（分别是接口或者父类，控制框架类要实现控制接口，让自己的内部事件类分别实现事件接口） 下面例子中分别是事件抽象类、控制类、控制框架类、测试类 // The common methods for any control event.事件抽象类 public abstract class Event {//本例中的事件全是简单的时间触发的，实际的事件类型会更多样 private long eventTime; protected final long delayTime; public Event(long delayTime) { this.delayTime = delayTime; start(); } public void start() { // Allows restarting eventTime = System.nanoTime() + delayTime; } public boolean ready() { return System.nanoTime() >= eventTime; } public abstract void action(); } ///:~ // The reusable framework for control systems.控制类 public class Controller { // A class from java.util to hold Event objects: private List<Event> eventList = new ArrayList<Event>(); public void addEvent(Event c) { eventList.add(c); } public void run() { while(eventList.size() > 0) // Make a copy so you're not modifying the list // while you're selecting the elements in it: for(Event e : new ArrayList<Event>(eventList)) if(e.ready()) { System.out.println(e); e.action(); eventList.remove(e); } } } ///:~ // This produces a specific application of the控制框架类 // control system, all in a single class. Inner // classes allow you to encapsulate different // functionality for each type of event. public class GreenhouseControls extends Controller { private boolean light = false; public class LightOn extends Event {//各种内部事件类在控制框架中的应用 public LightOn(long delayTime) { super(delayTime); } public void action() { // Put hardware control code here to // physically turn on the light. light = true; } public String toString() { return "Light is on"; } } public class LightOff extends Event { public LightOff(long delayTime) { super(delayTime); } public void action() { // Put hardware control code here to // physically turn off the light. light = false; } public String toString() { return "Light is off"; } } private boolean water = false; public class WaterOn extends Event { public WaterOn(long delayTime) { super(delayTime); } public void action() { // Put hardware control code here. water = true; } public String toString() { return "Greenhouse water is on"; } } public class WaterOff extends Event { public WaterOff(long delayTime) { super(delayTime); } public void action() { // Put hardware control code here. water = false; } public String toString() { return "Greenhouse water is off"; } } private String thermostat = "Day"; public class ThermostatNight extends Event { public ThermostatNight(long delayTime) { super(delayTime); } public void action() { // Put hardware control code here. thermostat = "Night"; } public String toString() { return "Thermostat on night setting"; } } public class ThermostatDay extends Event { public ThermostatDay(long delayTime) { super(delayTime); } public void action() { // Put hardware control code here. thermostat = "Day"; } public String toString() { return "Thermostat on day setting"; } } // An example of an action() that inserts a // new one of itself into the event list: public class Bell extends Event { public Bell(long delayTime) { super(delayTime); } public void action() { addEvent(new Bell(delayTime)); } public String toString() { return "Bing!"; } } public class Restart extends Event { private Event[] eventList; public Restart(long delayTime, Event[] eventList) { super(delayTime); this.eventList = eventList; for(Event e : eventList) addEvent(e); } public void action() {// 这个事件执行时会重置指定事件和它自己 for(Event e : eventList) { e.start(); // Rerun each event addEvent(e); } start(); // Rerun this Event addEvent(this); } public String toString() { return "Restarting system"; } } public static class Terminate extends Event { public Terminate(long delayTime) { super(delayTime); } public void action() { System.exit(0); } public String toString() { return "Terminating"; } } } ///:~ // Configure and execute the greenhouse system.测试类 // {Args: 5000} public class GreenhouseController { public static void main(String[] args) { GreenhouseControls gc = new GreenhouseControls(); // Instead of hard-wiring, you could parse // configuration information from a text file here: gc.addEvent(gc.new Bell(900));//这里往里面加事件是硬编码 Event[] eventList = {//更灵活的方式是从文件中读取需要的事件（方便修改） gc.new ThermostatNight(0), gc.new LightOn(200), gc.new LightOff(400), gc.new WaterOn(600), gc.new WaterOff(800), gc.new ThermostatDay(1400) }; gc.addEvent(gc.new Restart(2000, eventList)); if(args.length == 1) gc.addEvent( new GreenhouseControls.Terminate( new Integer(args[0]))); gc.run(); } } /* Output: Bing! Thermostat on night setting Light is on Light is off Greenhouse water is on Greenhouse water is off Thermostat on day setting Restarting system Terminating *///:~
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