Design-Pattern-Practice-/Behavioral-Design-Patterns-Note.txt at master · Mir00r/Design-Pattern-Practice- · GitHub

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					Behavioral
	-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*

		=> This design patterns is all about Class's objects communication. i.e How do you want a behavior in software?
		=> Behavioral patterns are about identifying common communication patterns between objects and realize these patterns.

1. Chain of Responsibility - A way of passing a request between a chain of objects

		Example: Loan or Leave approval process

		javax.servlet.Filter#doFilter()


2. Iterator - Sequentially access the elements of a collection

		Example: Next/Previous buttons on TV

		All implementations of java.util.Iterator & java.util.Enumeration


3. State - Alter an object's behavior when its state changes

		Example: A fan wall control


4. Observer - A way of notifying change to a number of classes

		Example: Bidding or auction

		Publish/Subscribe JMS API


5. Visitor - Defines a new operation to a class without change

		Example: Taxi


6. Template - Defer the exact steps of an algorithm to a subclass
		Example: A blueprint

		-> 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.
		-> JMSTemplate HibernateTemplate and JdbcTemplate in Spring


7. Command - Encapsulate a command request as an object

		Example: The "Guest Check" at a diner is an example of a Command pattern.
		The waiter or waitress takes an order or command from a customer and encapsulates that order by writing it on the check.
		The order is then queued for a short order cook. Note that the pad of "checks" used by each waiter is not dependent on the menu,
		and therefore they can support commands to cook many different items.

		All implementations of java.lang.Runnable


8. Memento - Capture and restore an object's internal state

		Example: save the state in a game & Undo/Redo operation in Windows

		All implementations of java.io.Serializable


9. Mediator - Defines simplified communication between classes

		Example: Air Traffic Controller(ATC)


10. Strategy - A Strategy defines a set of algorithms that can be used interchangeably.

		Example : Modes of transportation

		-> 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()