設(shè)計模式（Designpattern）是一套被反復(fù)使用、多數(shù)人知曉的、代碼、讓代碼更容易被他人理解、保證代碼可靠性。，設(shè)是工程的基石，同的一塊塊磚石一樣。項與描述了一個在周圍不斷重復(fù)發(fā)生的問題，以及該問題的決方案，這也是它能被廣泛用的原因。問題描述 Quacklogist中統(tǒng)計通知它的鴨子的個數(shù)，在一個中統(tǒng)計像鴨子一樣叫的bird的個數(shù)，對二者進(jìn)行比較。不使用設(shè)計模式的求解開發(fā)一個Duck鴨子模擬系開始選用繼承機制操作。定義一個鴨子抽象類別Duck,具有一些預(yù)設(shè)的鴨子動作方法swim()，fly(),quack(),以及一個顯示鴨子的方法display().衍生的實體鴨子類別（紅頭鴨，綠頭鴨）繼承Duck的各種動作，并復(fù)寫自己的現(xiàn)在系統(tǒng)加入一個新類別橡皮鴨RubberDuck,但事后橡皮鴨繼承了一個來自Duck的fly()方法，所以會發(fā)現(xiàn)應(yīng)該不會飛的RubberDuck現(xiàn)在可以飛來飛去。因為新加入的類別行為會改變，所以須將會變動的部分封代碼實現(xiàn)：從一Quackable定義一個鴨子接口，包含了對“鳴叫”的：packagepublicinterfacepublicvoidquack();}某些鴨子實Quackable接口：packageducks;publicclassMallardDuckimplements{publicvoidquack(){publicStringtoString(){return"MallardDuck";}}packagepublicclassRedheadDuckimplements{publicvoidquack(){publicStringtoString(){return"RedheadDuck";}}加入的鴨子packagepublicclassDuckCallimplements{publicvoidquack(){publicStringtoString(){return"DuckCall";}}packagepublicclassRubberDuckimplements{publicvoidquack(){publicStringtoString(){return"RubberDuck";}}創(chuàng)建鴨子模擬器packagepublicclassDuckSimulatorpublicstaticvoidmain(String[]args)DuckSimulatorsimulator=newDuckSimulator();voidsimulate()QuackablemallardDuck=newMallardDuck();QuackableredheadDuck=newRedheadDuck();QuackableduckCall=newDuckCall();QuackablerubberDuck=newRubberDuck();System.out.println("\nDuckSimulator");voidsimulate(Quackable{創(chuàng)建Birdpackagepublicclass{publicvoid{System.out.println("Honk");在這里采用適配器模式，使Bird與鴨子參雜在一packageadapter;publicclassBirpterimplements{protectedBirdpublicBirpter(Goose{this.goose=goose;}publicvoidquack(){publicStringtoString()return"Goosepretendingtobea模擬器中出現(xiàn)Bird：packageadapter;importducks.DuckCall;importducks.MallardDuck;importducks.Quackable;importducks.RedheadDuck;importducks.RubberDuck;publicclassDuckSimulator{publicstaticvoidmain(String[]{DuckSimulatorsimulator=newDuckSimulator();simulator.simulate();}voidsimulate()QuackablemallardDuck=newMallardDuck();QuackableredheadDuck=newRedheadDuck();QuackableduckCall=newDuckCall();QuackablerubberDuck=newRubberDuck();QuackablegooseDuck=newBirpter(newGoose());System.out.println("\nDuckSimulator:Withvoidsimulate(Quackable{實驗結(jié)果 ：這 packagedecorator;publicclassQuackCounterimplements{protectedQuackableduck;protectedstaticintnumberOfQuacks;publicQuackCounter(Quackableduck){this.duck=duck;}publicvoidquack(){publicstaticint{returnnumberOfQuacks;}publicStringtoString(){return更新模擬器，創(chuàng)建被裝飾的鴨packagedecorator;importadapter.Goose;importadapter.GooseAdapter;importducks.DuckCall;importducks.MallardDuck;importducks.Quackable;importducks.RedheadDuck;importducks.RubberDuck;publicclassDuckSimulator{publicstaticvoidmain(String[]{DuckSimulatorsimulator=newDuckSimulator();voidsimulate()QuackablemallardDuck=newQuackCounter(newQuackableredheadDuck=newQuackCounter(newQuackableduckCall=newQuackCounter(newQuackablerubberDuck=newQuackCounter(newQuackablegooseDuck=newSystem.out.println("\nDuckSimulator:WithSystem.out.println("Theducksquacked"+QuackCounter.getQuacks()+"times");}voidsimulate(Quackable{實驗結(jié)果此時又產(chǎn)生新的問題，能不能將創(chuàng)建鴨子們的程序都集中起來管理與包裝，此時需要工廠模式的介入：創(chuàng)建鴨子工packagefactory; {public createMallardDuck(); createRedheadDuck();public createDuckCall();public 創(chuàng)建工廠鴨packagefactory;importducks.DuckCall;importducks.Quackable;importducks.RubberDuckpublicclassDuckFactory {publicQuackablecreateMallardDuck(){returnnewMallardDuck();}publicQuackable{returnnewRedheadDuck();}publicQuackable{returnnewpublicQuackable{returnnewRubberDuck();}}packagefactory;importdecorator.QuackCounter;importducks.DuckCall;importducks.Quackable;importducks.RubberDuck;publicclassCountingDuckFactoryextendsDuckFactory{publicQuackablecreateMallardDuck()returnnewQuackCounter(newpublicQuackablecreateRedheadDuck()returnnewQuackCounter(newRedheadDuck());}publicQuackablecreateDuckCall(){returnnewQuackCounter(newDuckCall());}publicQuackablecreateRubberDuck(){returnnewQuackCounter(new使用模擬器來實驗該工廠鴨子packagefactory;importadapter.Goose;importadapter.GooseAdapter;importdecorator.QuackCounter;importducks.Quackable;publicclassDuckSimulator{publicstaticvoidmain(String[]{DuckSimulatorsimulator=newDuckSimulator();DuckFactoryduckFactory=newvoid DuckFactory{QuackablemallardDuck=QuackableredheadDuck=QuackableduckCall=duckFactory.createDuckCall();QuackablerubberDuck=QuackablegooseDuck=newGooseAdapter(newSystem.out.println("\nDuckSimulator:WithSystem.out.println("Theducksquacked"+QuackCounter.getQuacks()+"times");}voidsimulate(Quackableduck){實驗結(jié)果此時創(chuàng)建一群鴨子，使用集合的概念packageimportjava.util.ArrayList;importjava.util.Iterator;importducks.Quackable;publicclassFlockimplements{protectedArrayList<Quackable>quackers=publicvoidadd(Quackable{publicvoidquack()//迭代器模Iterator<Quackable>iterator=while(iterator.hasNext())Quackablequacker=iterator.next();publicString{return"Flockof修改模擬packagecomposite;importadapter.Goose;importadapter.GooseAdapter;importdecorator.QuackCounter;importducks.Quackable;importfactory.DuckFactory;importfactory.CountingDuckFactory;publicclassDuckSimulator{publicstaticvoidmain(String[]{DuckSimulatorsimulator=newDuckSimulator();DuckFactoryduckFactory=newvoid DuckFactory{QuackableredheadDuck=QuackableduckCall=duckFactory.createDuckCall();QuackablerubberDuck=QuackablegooseDuck=newGooseAdapter(newSystem.out.println("\nDuckSimulator:WithComposite-Flocks");FlockflockOfDucks=newFlock();FlockflockOfMallards=newFlock();QuackablemallardOne=QuackablemallardTwo=QuackablemallardThreeQuackablemallardFour=System.out.println("\nDuckSimulator:WholeFlockSystem.out.println("\nDuckSimulator:MallardFlockSimulation");System.out.println("\nTheducksquacked"++"voidsimulate(Quackable{實驗結(jié)果此時又該想到觀察個別鴨子的行為，能夠使用觀察者模式;定義Observer觀察者對象Observable中定義與觀察者方法，首先定義QuackObservable接口：packagepublicinterfaceQuackObservablepublicvoidregisterObserver(Observerobserver);publicvoidnotifyObservers();}Quackable實現(xiàn)該接口，同時Observable繼承接packageimportjava.util.Iterator;importjava.util.ArrayList;publicclassObservableimplements{ArrayList<Observer>observers=newQuackObservablepublicObservable(QuackObservable{this.duck=publicvoidregisterObserver(ObserverpublicvoidnotifyObservers(){Iterator<Observer>iterator=while(iterator.hasNext())Observerobserver=iterator.next();observer.update(duck)}}publicIterator<Observer>{return整合Observable與QuackablepackageimportpublicclassMallardDuck2extendsMallardDuckimplementsObservablepublicMallardDuck2()observable=newObservable(this);}publicvoidquack(){publicvoidregisterObserver(ObserverpublicvoidnotifyObservers(){ObserverpackagepublicinterfaceObserverpublicvoidupdate(QuackObservable需要一個觀察者監(jiān)督呱呱packagepublicclassQuackologistimplements{publicvoidupdate(QuackObservableduck)System.out.println("Quackologist:"+duck+"justpublicString{return更新模擬packageobserver;importadapter.Goose;publicclassDuckSimulatorpublicstaticvoidmain(String[]{DuckSimulatorsimulator=newDuckSimulator()