设计模式笔记(java版).docx

设计模式笔记1、 单例模式定义：确保一个类只有一个实例，并提供一个全局访问点。类图：源代码：public class Singleton private static Singleton instance = null;private Singleton()public static Singleton getInstance() if(instance = null)synchronized (Singleton.class) instance = new Singleton();return instance;2、 工厂模式定义：工厂模式定义了一个创建对象的接口，由子类决定要实例化的类是哪一个。工厂方法让类把实例化推迟到子类。(1). 简单工厂模式类图：源代码：public abstract class Product public void method1() public void method2() public class Product_A extends Productpublic Product_A() public void method1() System.out.println(this is method1 in Product_A);public void method2() System.out.println(this is method2 in Product_A);public class Product_B extends Productpublic Product_B() public void method1() System.out.println(this is method1 in Product_B);public void method2() System.out.println(this is method2 in Product_B);public class SimpleFactory public Product createProduct(String type) Product product = null;if(type.equals(Product_A)product = new Product_A();else if (type.equals(Product_B) product = new Product_B();return product;(2). 抽象工厂模式类图：源代码：public interface Product public void method1();public void method2();public class Product_A implements Product Overridepublic void method1() System.out.println(this is method1 in Product_A);Overridepublic void method2() System.out.println(this is method2 in Product_A);public class Product_B implements Product Overridepublic void method1() System.out.println(this is method1 in Product_B);Overridepublic void method2() System.out.println(this is method2 in Product_B);public interface AbstractFactory public Product getProduct();public class Product_A_Factoty implements AbstractFactory Overridepublic Product getProduct() return new Product_A();public class Product_B_Factory implements AbstractFactory Overridepublic Product getProduct() return new Product_B();3、 策略模式定义：策略模式定义了算法族，分别将其封装起来，让它们之间可以相互替换，此模式让算法的变化独立于使用算法的客户。类图：源代码：public abstract class Processor public Object process(Object obj)return obj; /* * ConcreteProcessor * */public class Upcase extends Processorpublic String process(Object obj)return (String)obj).toUpperCase(); /* * ConcreteProcessor * */public class Downcase extends Processorpublic String process(Object obj)return (String)obj).toLowerCase(); public class Strategy public void process(Processor p,Object obj) System.out.println(cess(obj);4、 观察者模式定义：观察者模式定义了对象之间的一对多依赖，这样一来，当一个对象改变状态时，它的所有依赖者都会收到通知并自动更新。类图：源代码：public interface Subject public void registerObserver(Observer o);public void removeObserver(Observer o);public void notifyObserver(); /当主题状态改变时，该方法会被调用，以通知所有的观察者public class ConcreteSubject implements Subject private List observers;private String parameter;public ConcreteSubject() this.observers = new ArrayList();Overridepublic void registerObserver(Observer o) this.observers.add(o);Overridepublic void removeObserver(Observer o) this.observers.remove(o);Overridepublic void notifyObserver() int i,n;n = this.observers.size();for(i = 0;i n;i+)Observer observer = this.observers.get(i);observer.update(parameter);public void setParameter(String parameter) this.parameter = parameter;notifyObserver();public interface Observer public void update(String parameter);public class ConcreteObserver implements Observer private String parameter;private Subject subject;public ConcreteObserver(Subject subject) this.subject = subject;this.subject.registerObserver(this);Overridepublic void update(String parameter) this.parameter = parameter;display();public void display() System.out.println(Current state : + parameter);5、 装饰者模式定义：动态地将责任附加到对象上。若要扩展功能，装饰着提供了比继承更有弹性的替代方法。类图：源代码：public abstract class Component protected String description = Component;public String getDescription() return description;public class ConcreteComponent_A extends Componentpublic ConcreteComponent_A() description = ConcreteComponent_A;public String getDescription() return description;public class ConcreteComponent_B extends Componentpublic ConcreteComponent_B() description = ConcreteComponent_B;public String getDescription() return description;public abstract class Decorator extends Componentpublic abstract String getDescription();public class ConcreteDecorator_A extends DecoratorComponent component;public ConcreteDecorator_A(Component component) ponent = component;Overridepublic String getDescription() return component.getDescription() + , ConcreteDecorator_A;public class ConcreteDecorator_B extends DecoratorComponent component;public ConcreteDecorator_B(Component component) ponent = component;Overridepublic String getDescription() return component.getDescription() + , ConcreteDecorator_B;6、 命令模式定义：将“请求”封装成对象，以便使用不同的请求、队列或日志来参数化其对象。命令模式也支持可撤销的操作。类图：源代码：public interface Command public void execute();/* 起到ConcreteCommand的作用 * */public class LightOnCommand implements Command private Light light;public LightOnCommand(Light light) this.light = light;Overridepublic void execute() light.on();/* 起到ConcreteCommand的作用 * */public class LightOffCommand implements Command private Light light;public LightOffCommand(Light light) this.light = light;Overridepublic void execute() light.off();/* 起到Receiver的作用 * */public class Light private boolean light;private String name;public Light(String name) = name;public void on() light = true;public void off() light = false;Overridepublic String toString() return Light name = + name + , is = + light + ;public class Invoker private Command onCommands;private Command offCommands;public Invoker() onCommands = new Command2;offCommands = new Command2;for(int i = 0;i 2;i+)onCommandsi = null;offCommandsi = null;public void setCommand(int index,Command on,Command off) onCommandsindex = on;offCommandsindex = off;public void onButtonWasPushed(int index) onCommandsindex.execute();public void offButtonWasPushed(int index) offCommandsindex.execute();Overridepublic String toString() String str = ;for(int i = 0;i onCommands.length;i+)str += index +i+ : +onCommandsi.getClass().getName()+ +offCommandsi.getClass().getName()+n;return str;7、 适配器模式定义：将一个类的接口，转换成客户期望的另一个接口。适配器让原本接口不兼容的类可以合作无间。类图：源代码:public interface Target public void request();public class RealTarget implements Target Overridepublic void request() System.out.println(this is real do.);public class Adaptee public void doing() System.out.println(this is Adaptee_do.);public class Adapter implements Target private Adaptee adaptee;public Adapter(Adaptee adaptee) this.adaptee = adaptee;Overridepublic void request() adaptee.doing();8、 外观模式定义：提供了一个统一的接口，用来访问子系统中的一群接口。外观定义了一个高层接口，让子系统更容易使用。类图：9、 模板方法模式定义：在一个方法中定义一个算法的骨架，而将一些步骤延迟到子类中。模板方法使得子类可以在不改变算法结构的情况下，重新定义算法中的某些步骤。类图：源代码：public abstract class AbstractClass final void templateMethod()primitiveOperation1();primitiveOperation2();abstract void primitiveOperation1();abstract void primitiveOperation2();public class ConcreteClass_A extends AbstractClassOverridevoid primitiveOperation1() System.out.println(this is primitiveOperation1 in ConcreteClass_A);Overridevoid primitiveOperation2() System.out.println(this is primitiveOperation2 in ConcreteClass_A);public class ConcreteClass_B extends AbstractClassOverridevoid primitiveOperation1() System.out.println(this is primitiveOperation1 in ConcreteClass_B);Overridevoid primitiveOperation2() System.out.println(this is primitiveOperation2 in ConcreteClass_B);10、 迭代器模式定义：提供一种方法顺序访问一个聚合对象中的各个元素，而又不暴露其内部的表示。作用：迭代器模式让我们能游走于聚合内的每一个元素，而又不暴露其内部的表示。将游走的任务放在迭代器上，而不是聚合上，这样简化了聚合的接口和实现，也让责任各得其所。类图：源代码：public interface Aggregate public Iterator createIterator(); /我们使用java.util.Iterator作为Iterator类public class ConcreteAggregate implements Aggregate List list;public ConcreteAggregate() this.list = new ArrayList();init();public void init() addItem(first);addItem(second);addItem(third);public void addItem(String parameter) list.add(parameter);Overridepublic Iterator createIterator() return list.iterator();11、 组合模式定义：允许将对象组合成树形结构来表现“整体/部分”层次结构。作用：组合能让客户以一致的方式处理个别对象以及对象组合。组合模式让我们能用树形方式创建对象的结构，树中包含了组合以及个别的对象。使用组合结构，我们能把相同的操作应用在组合和个别对象上。换句话说，在大多数情况下，我们可以忽略对象组合和个别对象之间的差异。类图：源代码：public abstract class Component public void add(Component component) throw new UnsupportedOperationException();public void remove(Component component) throw new UnsupportedOperationException();public Component getChild(int i) throw new UnsupportedOperationException();public void operation() public class Leaf extends Component String description;public Leaf(String description) this.description = description;public void operation() System.out.println(this is Leaf + description + operation.);public class Composite extends ComponentList components;String description;public Composite(String description) components = new ArrayList();this.description = description;public void add(Component component) components.add(component);public void remove(Component component) components.remove(component);public Component getChild(int i) return components.get(i);public void operation() System.out.println(this is Composite + description + operation.);12、 状态模式定义：允许对象在内部状态改变时