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。:)
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 onCharBuffer,ShortBuffer,IntBuffer,LongBuffer,FloatBufferandDoubleBuffer)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 onBoolean,Byte,Character,Short,Long,FloatandDouble)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 implementjava.lang.Cloneable)
Singleton (recognizable by creational methods returning the same instance (usually of itself) every time)
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()andsingletonXXX()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 onCharBuffer,ShortBuffer,IntBuffer,LongBuffer,FloatBufferandDoubleBuffer)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,ReaderandWriterhave a constructor taking an instance of same type. - Almost all implementations of
java.util.List,SetandMaphave a constructor taking an instance of same type. java.util.Collections, thecheckedXXX(),synchronizedXXX()andunmodifiableXXX()methods.javax.servlet.http.HttpServletRequestWrapperandHttpServletResponseWrapper
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 typesServletContext,LifeCycle,ViewHandler,NavigationHandlerand 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)
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.Proxyjava.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.
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)
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.Patternjava.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 alsojava.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.HttpSessionBindingListenerjavax.servlet.http.HttpSessionAttributeListenerjavax.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 byFacesServlet, 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.Readerandjava.io.Writer. - All non-abstract methods of
java.util.AbstractList,java.util.AbstractSetandjava.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.
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)
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