Creational patterns
Abstract factory
(recognizeable by creational methods returning the factory itself which in turn can be
used to create another abstract/interface type)
- javax.xml.parsers.DocumentBuilderFactory#newInstance()
- javax.xml.transform.TransformerFactory#newInstance()
- javax.xml.xpath.XPathFactory#newInstance()
Builder
(recognizeable 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
- java.util.stream.Stream.Builder
Factory method
(recognizeable by creational methods returning an implementation of an abstract/interface
type)
- java.util.Calendar#getInstance()
- java.util.ResourceBundle#getBundle()
- java.text.NumberFormat#getInstance()
- java.nio.charset.Charset#forName()
- java.net.URLStreamHandlerFactory#createURLStreamHandler(String) (Returns singleton object per protocol)
- java.util.EnumSet#of()
- javax.xml.bind.JAXBContext#createMarshaller() and other similar methods
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)
- java.util.Arrays#asList()
- java.util.Collections#list()
- java.util.Collections#enumeration()
- java.io.InputStreamReader(InputStream) (returns a Reader)
- java.io.OutputStreamWriter(OutputStream) (returns a Writer)
- javax.xml.bind.annotation.adapters.XmlAdapter#marshal() and #unmarshal()
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
Composite
(recognizeable by behavioral methods taking an instance of same abstract/interface type
into a tree structure)
- java.awt.Container#add(Component) (practically all over Swing thus)
- javax.faces.component.UIComponent#getChildren() (practically all over JSF UI thus)
Decorator
(recognizeable by creational methods taking an instance of same abstract/interface type
which adds additional behaviour)
- All subclasses of java.io.InputStream, OutputStream, Reader and Writer have a constructor taking an instance of same type.
- java.util.Collections, the checkedXXX(), synchronizedXXX() and unmodifiableXXX() methods.
- javax.servlet.http.HttpServletRequestWrapper and HttpServletResponseWrapper
- javax.swing.JScrollPane
Facade
(recognizeable by behavioral methods which internally uses instances of different
independent abstract/interface types)
- javax.faces.context.FacesContext, it internally uses among others the abstract/interface types LifeCycle, 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 uses ServletContext, HttpSession, HttpServletRequest, HttpServletResponse, etc.
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, Longand BigDecimal)
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)
- java.lang.reflect.Proxy
- java.rmi.*
- javax.ejb.EJB (explanation here)
- javax.inject.Inject (explanation here)
- javax.persistence.PersistenceContext
Behavioral patterns
Chain of responsibility
(recognizeable by behavioral methods which (indirectly) invokes the same method in another
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)
- java.util.Pattern
- java.text.Normalizer
- All subclasses of java.text.Format
- All subclasses of javax.el.ELResolver
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)
- 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
(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 longvalue)
- 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)
- 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
(recognizeable by behavioral methods which changes its behaviour depending on the
instance's state which can be controlled externally)
- javax.faces.lifecycle.LifeCycle#execute() (controlled by FacesServlet, the behaviour is dependent on current phase (state) of JSF lifecycle)
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)
- java.util.Comparator#compare(), executed by among others Collections#sort().
- javax.servlet.http.HttpServlet, the service() and all doXXX() methods take HttpServletRequest 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
(recognizeable by behavioral methods which already have a "default" behaviour defined by
an abstract type)
- 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 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 defined which
takes each the otherabstract/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 AnnotationValueVisitor
- javax.lang.model.element.Element and ElementVisitor
- javax.lang.model.type.TypeMirror and TypeVisitor
- java.nio.file.FileVisitor and SimpleFileVisitor
- javax.faces.component.visit.VisitContext and VisitCallback
Source: stackoverflow.com
