Patterns Used In Java | Newtonica

Patterns Used In Java

2 hours

oojava

designpatterns

Intermediate

developer

Creational patterns

Abstract factory

Builder

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

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

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

singleton

Structural patterns

Adapter

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

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

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

Decorator

All subclasses of java.io.InputStream, OutputStream, Reader and Writer, FilterInputStream have a constructor taking an instance of same or parent type.
java.util.Collections, the checkedXXX(), synchronizedXXX() and unmodifiableXXX() methods.
javax.servlet.http.HttpServletRequestWrapper and HttpServletResponseWrapper
javax.swing.JScrollPane

Facade

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

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

Proxy

Behavioral patterns

Chain of responsibility

Command

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

Interpreter

Iterator

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

Mediator

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

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

java.util.Observer/java.util.Observable
All implementations of java.util.EventListener (e.g. in Swing)
javax.servlet.http.HttpSessionBindingListener
javax.servlet.http.HttpSessionAttributeListener
javax.faces.event.PhaseListener

State

javax.faces.lifecycle.LifeCycle#execute() (controlled by FacesServlet, the behaviour is dependent on current phase (state) of JSF lifecycle)

Strategy

java.util.Comparator#compare(), e.g. executed by List#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

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.

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