pattern in JDK_this interface has been encapsulated other type al-优快云博客

本文列举了JDK中各种设计模式的应用实例，包括创建型、结构型和行为型模式，如单例模式的java.lang.Runtime#getRuntime()，适配器模式的java.io.InputStreamReader(InputStream)，以及迭代器模式的java.util.Iterator等。

Creational patterns

Abstract factory ^{_{(recognizeable by creational methods returning an abstract/interface type)}}

Builder ^{_{(recognizeable by creational methods returning the instance itself)}}

Factory method ^{_{(recognizeable by creational methods returning a concrete type)}}

Prototype ^{_{(recognizeable 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 ^{_{(recognizeable by creational methods returning the same instance (usually of itself) everytime)}}

Structural patterns

Adapter ^{_{(recognizeable 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)}}

Bridge ^{_{(recognizeable 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 ^{_{(recognizeable by behavioral methods taking an instance of same abstract/interface type)}}

Decorator ^{_{(recognizeable 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 ^{_{(recognizeable by behavioral methods which internally uses instances of different independent abstract/interface types)}}

Flyweight ^{_{(recognizeable by creational methods returning a cached instance, a bit the "multiton" idea)}}

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

Proxy ^{_{(recognizeable 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)}}

^{_{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 ^{_{(recognizeable by behavioral methods which (indirectly) invokes the same method inanother implementation of same abstract/interface type in a queue)}}

Command ^{_{(recognizeable 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 ^{_{(recognizeable 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)}}

Iterator ^{_{(recognizeable by behavioral methods sequentially returning instances of a different type from a queue)}}

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

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

Memento ^{_{(recognizeable 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) ^{_{(recognizeable by behavioral methods which invokes a method on an instance of another abstract/interface type, depending on own state)}}

State ^{_{(recognizeable by behavioral methods which changes its behaviour depending on the instance's state which can be controlled externally)}}

Strategy ^{_{(recognizeable 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)}}

Template method ^{_{(recognizeable by behavioral methods which already have a "default" behaviour definied 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 ^{_{(recognizeable by two different abstract/interface types which has methods definied which takes each theother 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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下面是JDK中有关23个经典设计模式的示例，在stakeoverflow也有相应的讨论：
http://stackoverflow.com/questions/1673841/examples-of-gof-design-patterns