JDK (SE， EE)中的GOF模式。

引子：Stack Overflow的一个问题，不过写的太全面了。:)

http://stackoverflow.com/questions/1673841/examples-of-gof-design-patterns

 

Creational patterns

Abstract factory (recognizable by creational methods returning an abstract/interface type)

• java.util.Calendar#getInstance()
• java.util.Arrays#asList()
• java.util.ResourceBundle#getBundle()
• java.net.URL#openConnection()
• java.sql.DriverManager#getConnection()
• java.sql.Connection#createStatement()
• java.sql.Statement#executeQuery()
• java.text.NumberFormat#getInstance()
• java.lang.management.ManagementFactory (all getXXX() methods)
• java.nio.charset.Charset#forName()
• javax.xml.parsers.DocumentBuilderFactory#newInstance()
• javax.xml.transform.TransformerFactory#newInstance()
• javax.xml.xpath.XPathFactory#newInstance()

Builder (recognizable by creational methods returning the instance itself)

• java.lang.StringBuilder#append() (unsynchronized)
• java.lang.StringBuffer#append() (synchronized)
• java.nio.ByteBuffer#put() (also on CharBuffer, ShortBuffer, IntBuffer, LongBuffer,FloatBuffer and DoubleBuffer)
• javax.swing.GroupLayout.Group#addComponent()
• All implementations of java.lang.Appendable

Factory method (recognizable by creational methods returning a concrete type)

• java.lang.Object#toString() (overridable in all subclasses)
• java.lang.Class#newInstance()
• java.lang.Integer#valueOf(String) (also on Boolean, Byte, Character, Short, Long,Float and Double)
• java.lang.Class#forName()
• java.lang.reflect.Array#newInstance()
• java.lang.reflect.Constructor#newInstance()

Prototype (recognizable by creational methods returning a different instance of itself with the same properties)

• java.lang.Object#clone() (the class has to implement java.lang.Cloneable)

Singleton (recognizable by creational methods returning the same instance (usually of itself) every time)

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

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Structural patterns

Adapter (recognizable by creational methods taking an instance of different abstract/interface type and returning an implementation of own/another abstract/interface type which decorates/overrides the given instance)

• java.io.InputStreamReader(InputStream) (returns a Reader)
• java.io.OutputStreamWriter(OutputStream) (returns a Writer)
• javax.xml.bind.annotation.adapters.XmlAdapter#marshal() and #unmarshal()

Bridge (recognizable by creational methods taking an instance of different abstract/interface type and returning an implementation of own abstract/interface type which delegates/uses the given instance)

• 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, but uses them. The java.util.Collections#newSetFromMap() and singletonXXX() methods however comes close.

Composite (recognizable by behavioral methods taking an instance of same abstract/interface type)

• java.util.Map#putAll(Map)
• java.util.List#addAll(Collection)
• java.util.Set#addAll(Collection)
• java.nio.ByteBuffer#put(ByteBuffer) (also on CharBuffer, ShortBuffer, IntBuffer,LongBuffer, FloatBuffer and DoubleBuffer)
• java.awt.Container#add(Component) (practically all over Swing thus)

Decorator (recognizable by creational methods taking an instance of same abstract/interface type)

• All subclasses of java.io.InputStream, OutputStream, Reader and Writer have a constructor taking an instance of same type.
• Almost all implementations of java.util.List, Set and Map have a constructor taking an instance of same type.
• java.util.Collections, the checkedXXX(), synchronizedXXX() and unmodifiableXXX() methods.
• javax.servlet.http.HttpServletRequestWrapper and HttpServletResponseWrapper

Facade (recognizable by behavioral methods which internally uses instances of different independent abstract/interface types)

• javax.faces.webapp.FacesServlet, it internally uses under each the abstract/interface types ServletContext, LifeCycle, ViewHandler, NavigationHandler and many more without that the end-user has to worry about it (which are however overridable by injection).

Flyweight (recognizable by creational methods returning a cached instance, a bit the “multiton” idea)

• java.lang.Integer#valueOf(int) (also on Boolean, Byte, Character, Short, Long, Float and Double)

Proxy (recognizable by creational methods which returns an implementation of given abstract/interface type which in turn delegates/uses a different implementation of given abstract/interface type)

• java.lang.reflect.Proxy
• java.rmi.*, the whole API actually.

The Wikipedia example is IMHO a bit poor, lazy loading has actually completely nothing to do with the proxy pattern at all.

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Behavioral patterns

Chain of responsibility (recognizable by behavioral methods which (indirectly) invokes the same method in another implementation of same abstract/interface type in a queue)

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

Command (recognizable by behavioral methods in an abstract/interface type which invokes a method in an implementation of a different abstract/interface type which has been encapsulated by the command implementation during its creation)

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

Interpreter (recognizable by behavioral methods returning a structurally different instance/type of the given instance/type; note that parsing/formatting is not part of the pattern, determining the pattern and how to apply it is)

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

Iterator (recognizable by behavioral methods sequentially returning instances of a different type from a queue)

• All implementations of java.util.Iterator (thus under each also java.util.Scanner!).
• All implementations of java.util.Enumeration

Mediator (recognizable by behavioral methods taking an instance of different abstract/interface type (usually using the command pattern) which delegates/uses the given instance)

• java.util.Timer (all scheduleXXX() methods)
• java.util.concurrent.Executor#execute()
• java.util.concurrent.ExecutorService (the invokeXXX() and submit() methods)
• java.util.concurrent.ScheduledExecutorService (all scheduleXXX() methods)
• java.lang.reflect.Method#invoke()

Memento (recognizable by behavioral methods which internally changes the state of the whole instance)

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

Observer (or Publish/Subscribe) (recognizable by behavioral methods which invokes a method on an instance of another abstract/interface type, depending on own state)

• 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

State (recognizable by behavioral methods which changes its behavior depending on the instance’s state which can be controlled externally)

• All implementations of java.util.Iterator
• javax.faces.lifecycle.LifeCycle#execute() (controlled by FacesServlet, the behavior is dependent on current phase (state) of JSF lifecycle)

Strategy (recognizable by behavioral methods in an abstract/interface type which invokes a method in an implementation of a different abstract/interface type which has been passed-in as method argument into the strategy implementation)

• java.util.Comparator#compare(), executed by under each Collections#sort().
• javax.servlet.http.HttpServlet, the service() and all doXXX() methods takeHttpServletRequest and HttpServletResponse and the implementor has to process them (and not to get hold of them as instance variables!).
• javax.servlet.Filter#doFilter()

Template method (recognizable by behavioral methods which already have a “default” behavior defined by an abstract type)

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

Visitor (recognizable by two different abstract/interface types which has methods defined which takes each the other abstract/interface type; the one actually calls the method of the other and the other executes the desired strategy on it)

• javax.lang.model.element.AnnotationValue and javax.lang.model.element.AnnotationValueVisitor
• javax.lang.model.element.Element and javax.lang.model.element.ElementVisitor
• javax.lang.model.type.TypeMirror and javax.lang.model.type.TypeVisitor