观察者模式定义了一种一对多的依赖关系, 让多个观察对像同时监听某一个对象, 这个对象在改变时会通知所有观察者。 代码 1 在这个小例子中, 由间谍 spy 扮演被观察者窃取, 当间谍发现甲国家的秘密信息后它的状态改变, 然后通知扮演观察者的乙丙国, 乙丙国在收到 spy 的信息后会做出不一样的判断。 1public abstract class Country { 2 protected String countryName; 3 protected Spy007 spy; 4 5 public Country(String countryName, Spy007 spy) { 6 this.countryName = countryName; 7 this.spy = spy; 8 } 9 10 public abstract void update(); 11} 1public class CountryA extends Country{ 2 3 public CountryA(String countryName, Spy007 spy) { 4 super(countryName, spy); 5 } 6 7 /** 8 * 获取情报的方

在状态模式中，当一个对象的内在状态改变时允许改变其行为, 这个对象看起来像是改变了它的类。 代码 1public abstract class State { 2 public String stateName; 3 public abstract void handle(Context context); 4} 1public class Context { 2 private State state; 3 4 public Context(State state) { 5 this.state = state; 6 } 7 8 public void setState(State state) { 9 10 System.out.println("当前状态为: "+this.state.stateName); 11 this.state = state; 12 System.out.println("状态变更为: "+this.state.stateName); 13 System.out.println("--------------------"); 14 } 15 16 public void request(){ 17 state.handle(this); 18 } 19} 1public class ConcreteStateA extends State { 2 public ConcreteStateA(){ 3 stateName = "状态A"; 4 }

策略模式定义了算法家族, 分别封装起来, 让他们之间可以相互替换, 此模式让算法的变化影响到使用的客户。 代码 1public interface Strategy { 2 void Algorithm(); 3} 1public class StrategyA implements Strategy { 2 @Override 3 public void Algorithm() { 4 System.out.println("使用了StrategyA的算法"); 5 } 6} 1public class StrategyB implements Strategy{ 2 @Override 3 public void Algorithm() { 4 System.out.println("使用了StrategyB的算法"); 5 } 6} 1public class Context{ 2 Strategy strategy; 3 4 public Context(Strategy strategy) { 5 this.strategy = strategy;

模板方法（TemplateMethod）定义一个操作中的算法的骨架, 而将一些步骤延迟到子类中, 使得子类可以不改变一个算法的结构即可重新定义算法的某些特定的步骤。 类关系 1 +--------------------+ 2 | AbstractClass | 3 +-^-----------^------+ 4 extends | | 5 +----+ +--+ extends 6 | | 7+--------+--------+ +-----+------------+ 8| ImplClassA | | ImplClassB | 9+-----------------+ +------------------+ 1public abstract class AbstractClass { 2 abstract void methodA(); 3 4 abstract void methodB(); 5 6 abstract void methodC(); 7 8 void executeTemplateMethod() { 9 methodA(); 10 methodB(); 11 methodC(); 12 } 13} 1public class ImplClassA extends AbstractClass { 2 @Override 3 void methodA() { 4 System.out.println("ClassA的methodA方法执行

代理模式：为其他对象提供一种代理以控制对这个对象的访问。 静态代理的关键：代理类(SubjectProxy)实现被代理类的接口(ISubject)。 类结构 1 +-------------+ 2 | | 3 | ISubject interface 4 | | 5 +-^---------^-+ 6 | | 7 implement |implement 8 | | 9 | | 10+--------------+-+ ++--------------+ 11| | | | 12| SubjectProxy | | Subject | 13+----------------+ +---------------+ 代码 1public interface ISubject { 2 void request(); 3} 1public class Subject implements ISubject { 2 @Override 3 public void request() { 4 System.out.println("Subject的request方法执行了."); 5 } 6} 1public class SubjectProxy implements ISubject

外观模式为子系统的中的一组接口提供一个一致的界面, 此模式定义了一个高层接口个, 这个接口使子系统更加容易使用。 其本质是：方法调用再封装。 代码 1public class SubA { 2 void methodA(){ 3 System.out.println("SubA的methodA执行了."); 4 } 5} 6 7public class SubB { 8 void methodB(){ 9 System.out.println("SubB的方法methodB执行了."); 10 } 11} 12 13public class SubC { 14 void methodC(){ 15 Sys

运用享元模式（Flyweight）可以有效地支持大量细粒度的对象。 类结构 代码 1package com.elltor.designpattern.Flyweight; 2 3public interface Flyweight { 4 void operation(int i); 5} 1package com.elltor.designpattern.Flyweight; 2 3public class ConcreteFlyweight implements Flyweight { 4 5 @Override 6 public void operation(int i) { 7 System.out.println("具体的享元对象: "+i); 8 } 9} 1package com.elltor.designpattern.Flyweight; 2 3import java.util.HashMap; 4 5public class FlyweightFcatory { 6 private HashMap<String,ConcreteFlyweight> flyweightMap = new HashMap<>(); 7 8 public FlyweightFcatory() { 9 flyweightMap.put("A",new ConcreteFlyweight()); 10 flyweightMap.put("B",new ConcreteFlyweight()); 11 flyweightMap.put("C",new ConcreteFlyweight()); 12 flyweightMap.put("D",new ConcreteFlyweight()); 13 flyweightMap.put("E",new ConcreteFlyweight()); 14 } 15 16 public Flyweight getFlyweight(String key){ 17 return flyweightMap.get(key); 18 } 19} 1package com.elltor.designpattern.Flyweight; 2 3public class UnsharedFlyweight implements Flyweight { 4 @Override 5 public void operation(int i) { 6 System.out.println("不被

组合模式适合表示部分-整体, 例如大学-院系、部门-企业等。 类结构 代码 1package com.elltor.designpattern.compose; 2 3public abstract class Component { 4 protected String componentName; 5 6 7 public Component(String componentName) { 8 this.componentName = componentName; 9 } 10 11 public abstract void add(Component component); 12 13 public abstract void remove(Component component); 14 15 public abstract void show(int depth); 16} 1package com.elltor.designpattern.compose; 2 3import java.util.ArrayList; 4import java.util.List; 5 6public class Composite extends Component { 7 private List<Component> childList = new ArrayList<>(); 8 9 public Composite(String componentName) { 10 super(componentName); 11 } 12 13 @Override 14 public void add(Component component) { 15 childList.add(component); 16 } 17 18 @Override 19 public void remove(Component component) { 20 childList.remove(component); 21 } 22 23 @Override 24 public void show(int depth) { 25 for(int i=0;i<depth;i++){ 26 System.out.print('+'); 27 } 28 29 System.out.println(componentName); 30 31 for(int i=0;i<childList.size();i++){ 32 childList.get(i).show(depth+2); 33 } 34 } 35} 1package com.elltor.designpattern.compose; 2 3public class Leaf extends Component { 4 public Leaf(String componentName) { 5 super(componentName); 6 } 7 8 @Override 9 public void add(Component component) { 10 Syst

结构图 代码 1package com.elltor.designpattern.decorate; 2 3public interface Component { 4 void operate(); 5} 1package com.elltor.designpattern.decorate; 2 3public class ConcreteComponent implements Component { 4 @Override 5 public void operate() { 6 System.out.println("ConcreteComponent operate....(origin)"); 7 } 8} 1package com.elltor.designpattern.decorate; 2 3public class Decorator implements Component { 4 protected Component component; 5 6 public void setComponent(Component component){ 7 this.component=component; 8 } 9 10 11 @Override 12 public void operate() { 13 if(this.component!=null){ 14 component.operate(); 15 } 16 } 17} 1package com.elltor.designpattern.decorate; 2 3public class Decorator implements Component { 4 protected Component component; 5 6 public void setComponent(Component component){ 7 this.component=component; 8 } 9 10 11 @Override 12 public void operate() { 13 if(this.component!=null){ 14 component.operate(); 15 } 16 } 17} 1package com.elltor.designpattern.decorate; 2 3public class ConcreteDecoratorA extends Decorator { 4 String info = "ConcreteDecoratorA"; 5 6 7 // 并不太好 8 @Override 9 public void operate() { 10 super.operate(); 11 System.out.println("装饰一下..............")