Dinesh on Java

Behavioral design pattern deals with the communication between class objects. They are used to sense the presence of already present communication patterns and may be able to manipulate these patterns. Behavioral pattern is a design pattern through which common communication patterns are identified between different objects. This way the communication is carried out in more flexible way.

Behavioral design pattern

Patterns under this category, characterize the ways in which classes or objects interact and distribute responsibility. These design patterns are specifically concerned with communication between objects. So here, you will learn how to use behavioral patterns to reduce complicated flow control. Furthermore, you will use behavioral patterns to encapsulate algorithms and dynamically select them at run time.

This module explores different behavioral design patterns, patterns that describe the way objects and classes interact and divide responsibilities among themselves. A behavioral pattern abstracts an action you want to take from the object or class that takes the action. By changing the object or class, you can change the algorithm used, the objects affected, or the behavior, while still retaining the same basic interface for client classes.

A good toolbox of behavioral patterns allows you to solve many challenging problems you are likely to encounter when designing object-oriented systems. These include enumerating lists, responding to changes of state in an object, serializing and deserializing objects without penetrating data encapsulation.

In this module, you will learn:

• How programmers use behavioral design patterns
• About the most commonly used design patterns
• When to use the Observer and Mediator patterns
• How to use the Mediator pattern to manage the different traffic lights

Behavioral object patterns use object composition rather than inheritance. Some of these patterns describe how a group of peer objects cooperate to perform a task that no single object can carry out by itself. An important issue here is how peer objects know about each other. Peers could maintain explicit references to each other, but that would increase their coupling. In the extreme, every object would know about every other. The Mediator pattern avoids this by introducing a mediator object between peers. The mediator provides the indirection needed for loose coupling.

Patterns under Behavioral Design Pattern

Patterns under this category of the Behavioral Design Pattern, characterize the ways in which classes or objects interact and distribute responsibility. These design patterns are specifically concerned with communication between objects. So here, you will learn how to use behavioral patterns to reduce complicated flow control. Furthermore, you will use behavioral patterns to encapsulate algorithms and dynamically select them at run time. There are following listed design patterns come into this category.

Chain of responsibility

A chain of objects is created to deal with the request so that no request goes back unfulfilled.

Command

Command pattern deals with requests by hiding it inside an object as a command and sent to be to invoker object which then passes it to an appropriate object that can fulfill the request.

Interpreter

Interpreter pattern is used for language or expression evaluation by creating an interface that tells the context for interpretation.

Iterator

Iterator pattern is used to provide sequential access to a number elements present inside a collection object without any relevant information exchange.

Mediator

Mediator pattern provides easy communication through its mediator class that allows communication for several classes.

Memento

This pattern involves the working of three classes Memento, CareTaker, and Originator. Memento holds the restorable state of the object. Originator’s job is the creation and storing of state and CareTaker’s job is the restoration of memento states.

Null Object

Null Object is used instead of specifying a Null value and is used to represent a particular operation that does nothing when created. It is basically a check for Null value without the presence of the value.

Observer

A One-to-Many relationship calls for the need of Observer pattern to check the relative dependencies of objects.

State

In State pattern, the behavior of a class varies with its state and is thus represented by the context object.

Strategy

Strategy pattern deals with the change in class behavior at runtime. The objects consist of strategies and the context object judges the behavior at runtime of each strategy.

Template method

It is used with components having similarity where a template of the code may be implemented to test both the components. The code can be changed with minor alterations.

Visitor

A Visitor performs a set of operations on an element class and changes its behavior of execution. Thus the variance in the behavior of element class is dependent on the change in visitor class.