在Java 核心类库中关于GOF设计模式的例子

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原文地址：http://blog.csdn.net/jiangkai528/article/details/45195915

在Java 核心类库中关于GOF设计模式的例子

问题：我正在学习GOF的java 设计模式，我想找一些它们中鲜活的例子，在java 核心类库中有哪些好的例子呢？

回答：你可以在维基百科上获得许多设计模式概述。同时也会提到哪些是由GOF提出的。在这里我总结一下，我尽可能多的从java SE 和java EE 的 API 中选取一些设计模式的实现

1.抽象工厂模式（abstract factory）

javax.xml.parsers.DocumentBuilderFactory#newInstance()
javax.xml.transform.TransformerFactory#newInstance()
javax.xml.xpath.XPathFactory#newInstance()

2.生成器模式(builder)

java.lang.StringBuilder#append() (不同步，线程不安全)
java.lang.StringBuffer#append() (同步的，线程安全)
java.nio.ByteBuffer#put() (同时还有CharBuffer,ShortBuffer,IntBuffer,LongBuffer,FloatBufferand DoubleBuffer)
javax.swing.GroupLayout.Group#addComponent()
java.lang.Appendable 的所有实现类

3. 工厂方法模式(factory method)

java.util.Calendar#getInstance()
java.util.ResourceBundle#getBundle()
java.text.NumberFormat#getInstance()
java.nio.charset.Charset#forName()
java.net.URLStreamHandlerFactory#createURLStreamHandler(String) (每次协议返回单个对象)

4. 原型模式(prototype)

java.lang.Object#clone() (这个类必须实现 java.lang.Cloneable 接口)

5.单例模式（singleton）

java.lang.Runtime#getRuntime()
java.awt.Desktop#getDesktop()

6.适配器模式（adapter)

java.util.Arrays#asList()
java.io.InputStreamReader(InputStream) (returns aReader)
java.io.OutputStreamWriter(OutputStream) (returns aWriter)
javax.xml.bind.annotation.adapters.XmlAdapter#marshal() and#unmarshal()

7. 桥接模式(bridge)

None comes to mind yet. A fictive example would be new LinkedHashMap(LinkedHashSet<K>, List<V>) which returns an unmodifiable linked map which doesn't clone the items, butuses them. Thejava.util.Collections#newSetFromMap() and singletonXXX() methods however comes close.

8.组合模式（composite)

java.awt.Container#add(Component) (practically all over Swing thus)
javax.faces.component.UIComponent#getChildren() (practically all over JSF UI thus)

9.装饰模式（decorator）

All subclasses of java.io.InputStream, OutputStream, Reader and Writer have a constructor taking an instance of same type.
java.util.Collections, thecheckedXXX(),synchronizedXXX() and unmodifiableXXX() methods.
javax.servlet.http.HttpServletRequestWrapper andHttpServletResponseWrapper

10.外观模式（facade)

javax.faces.context.FacesContext, it internally uses among others the abstract/interface typesLifeCycle,ViewHandler,NavigationHandler and many more without that the enduser has to worry about it (which are however overrideable by injection).
javax.faces.context.ExternalContext, which internally usesServletContext,HttpSession,HttpServletRequest,HttpServletResponse, etc.

11.享元模式（flyweight）

java.lang.Integer#valueOf(int) (同时还有Boolean,Byte,Character,Short and Long)

12.代理模式（proxy)

java.lang.reflect.Proxy
java.rmi.*, 整个API

13. 职责链模式（chain of responsibility）

java.util.logging.Logger#log()
javax.servlet.Filter#doFilter()

14. 命令模式（command)

All implementations of java.lang.Runnable
All implementations of javax.swing.Action

15. 解析器模式（interpreter)

java.util.Pattern
java.text.Normalizer
All subclasses of java.text.Format
All subclasses of javax.el.ELResolver

16. 迭代器模式（iterator）

All implementations of java.util.Iterator (thus among others also java.util.Scanner!).
All implementations of java.util.Enumeration

17. 中介者模式（mediator)

java.util.Timer (allscheduleXXX() methods)
java.util.concurrent.Executor#execute()
java.util.concurrent.ExecutorService (theinvokeXXX() andsubmit() methods)
java.util.concurrent.ScheduledExecutorService (allscheduleXXX() methods)
java.lang.reflect.Method#invoke()

18.备忘录模式（memento）

java.util.Date (the setter methods do that,Date is internally represented by along value)
All implementations of java.io.Serializable
All implementations of javax.faces.component.StateHolder

19. 观察者模式（observer)

java.util.Observer/java.util.Observable (rarely used in real world though)
All implementations of java.util.EventListener (practically all over Swing thus)
javax.servlet.http.HttpSessionBindingListener
javax.servlet.http.HttpSessionAttributeListener
javax.faces.event.PhaseListener

20.状态模式（state）

javax.faces.lifecycle.LifeCycle#execute()

(controlled by FacesServlet, the behaviour is dependent on current phase (state) of JSF lifecycle)

21.策略模式（strategy）

java.util.Comparator#compare(), executed by among othersCollections#sort().
javax.servlet.http.HttpServlet, theservice() and alldoXXX() methods takeHttpServletRequestandHttpServletResponse and the implementor has to process them (and not to get hold of them as instance variables!).
javax.servlet.Filter#doFilter()

22. 模板方法模式（template method）

All non-abstract methods of java.io.InputStream, java.io.OutputStream, java.io.Reader and java.io.Writer.
All non-abstract methods of java.util.AbstractList, java.util.AbstractSet and java.util.AbstractMap.
javax.servlet.http.HttpServlet, all thedoXXX() methods by default sends a HTTP 405 "Method Not Allowed" error to the response. You're free to implement none or any of them.