2) All of them uses Composition and delegation to fulfill there intent. Decorator supports recursive composition, which isn't possible with pure Adapters. The decorator pattern is an alternative to subclassing. The decorator pattern is somewhat similar to the adapter pattern, where one service “wraps” another. This type of design pattern comes under creational pattern as this pattern provides one of the best ways to create an object. The decorator pattern can be used to make it possible to extend (decorate) the functionality of a certain object at runtime. ... Adapter changes the interface of an existing object, while Decorator enhances an object without changing its interface. In Factory pattern, we create object without exposing the creation logic to the client and refer to newly created object using a common interface. Adapter design pattern is a structural pattern.Adapter pattern lets two components work together which have incompatible interfaces.It is useful if we need to implement some functionality in our application and a class already exists which provides the required functionality.But The existing class providing the required functionality has a different interface than … Decorator is a structural design pattern that lets you attach new behaviors to objects by placing these objects inside special wrapper objects that contain the behaviors. Adapter Design Pattern. This article discusses patterns called Adapter and Decorator, which come from Volume 1 of Patterns in Java. However, in contrast to adapters, decorators expose the same service as what they’re decorating. Decorator Design Pattern Intent. For a detailed description and implementation, have a look at the dedicated post: Adapter Pattern in Java Decorators¶. 1) All of them are defined as structural patterns as GOF design pattern in there classic book Java Design Patterns. Table of Contents. The decorator pattern can be used to extend (decorate) the functionality of a certain object statically, or in some cases at run-time, independently of other instances of the same class, provided some groundwork is done at design time.This is achieved by designing a new Decorator class that wraps the original class. Composite and Decorator have similar structure diagrams, reflecting the fact that both rely on recursive composition to organize an open-ended number of objects. Decorator design pattern is one of the structural design pattern (such as Adapter Pattern, Bridge Pattern, Composite Pattern) and uses abstract classes or interface with composition to implement. "Adapter makes things work after they're designed; Bridge makes them work before they are. The Adapter design pattern is meant to 'translate' the interface of one or more classes into an interface that the client expects to use -- the adapter would translate the calls to the expected interface into the actual interface the wrapped classes use. 1 Decorator Design Pattern; 2 Decorator Design Pattern – Class Diagram. An Adapter wraps an existing class with a new interface so that it becomes compatible with the interface needed. The Adapter pattern is used for connecting two incompatible interfaces that otherwise cannot be connected directly. The point of using decorators is to add functionality to an object without changing the object’s signature. This wrapping could be achieved by the following sequence of steps: This type of design pattern comes under structural pattern as this pattern acts as a wrapper to existing class. Decorator pattern allows a user to add new functionality to an existing object without altering its structure. For instance, we have a SuperWeaponsArray which can control a fine array of doomsday devices. Honestly, many patterns could be implemented the same way programmatically -- the difference is in intent. Factory pattern is one of most used design pattern in Java. [GoF, p219]" Effectively, the Adapter pattern is useful when you have existing code, be it third party, or in-house, but out of your control, or otherwise not changeable to quite meet the interface you need it to. These patterns are in the same article because they are structurally similar.