Composite Design Pattern Example

Composite Design Pattern: Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly. --By GOF BOOK

A composite is an object designed as a composition of one-or-more similar objects, all exhibiting similar functionality and also shows the 1-to-many  relationship or parent child  hierarchy.

Problem: In an application if we need to represent a parent and child, node and leaf hierarchy or a tree structure. Then it is difficult to represent these structures in traditional way.

Solution: By using Composite pattern it is very easy to build these kind of hierarchy or tree structure.

This pattern is very useful, especially when you building a user interface. You can treat display object and display container object the same way, without considering the differences between the two objects. It’s very common in the GUI building environment.

Composite can be used when clients should ignore the difference between compositions of objects and individual objects. If you find that you are using multiple objects in the same way, and they often have nearly identical code to handle each of them, then composite is a good choice for you. it is less complex in this situation to treat primitives and composites as homogeneous (Node)...

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Prototype Design Pattern Example

Prototype Design Pattern: Prototype design pattern is a creational design pattern and it is a template for creating an object from an already existing object. 

In this design pattern you use an already existing object as a prototype for creating a new object. If creating an object is time consuming, and if your application needs multiple such objects which are exactly the same or slightly different then you can use prototype pattern.

Prototype pattern can be used in transactional system, where in before performing a transaction, a clone of the prototype object is created, transaction is performed on the cloned object and if the transaction is successful  the prototype is replaced with cloned object by making the cloned object as the prototype. In case if transaction fails then the cloned object can be completely discarded.

The prototype object holds certain amount of information and if you need a similar object you can then clone the prototype object to create a similar object. If you application requires similar object but differ slightly then you can clone the prototype object and modify it slightly to fit the need of the application.

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Java Developer Tools

Java Developer Tools:

Oracle has released Java 7 update 40, with some major new features in JDK 7 Update 40 (7u40) release. Java Mission Control is bundled with this JDK release a JVM monitoring tool, Rule Sets for Java applets and Web Start applications, and a lots of bug fixes.

Mission Control

Java Flight Recorder and Java Mission Control together create a complete tool chain to continuously collect low level and detailed runtime information enabling after-the-fact incident analysis. Java Flight Recorder is a profiling and event collection framework built into the Oracle JDK. It allows Java administrators and developers to gather detailed low level information about how the Java Virtual Machine (JVM) and the Java application are behaving.

Using the Java SE Advanced and Java SE Suite you can do the following

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Abstract Factory Design Pattern Example

Abstract Factory Design Pattern: Provide an interface for creating families of related or dependent objects without specifying their concrete classes -- By THE GOF BOOK.

The abstract factory pattern is an extension of the  Factory Method pattern. Both are about creating the new objects, while abstract factory cares more about a family of objects or products to be produced.

In simple words, A normal factory is used to create sets of related or similar objects and an abstract factory is used to return instance of factories. Thus, we can say, an abstract factory is used to return instance of factories that can be used to create similar or related objects.

As there is a ‘abstract’ word in the pattern name don’t mistake and confuse it with java ‘abstract’ keyword. It is not related to that. This abstract is for abstraction from object oriented programming point of view.

Lets understand this with a simple example.

Problem: As in my previous post  Factory Method pattern, we created a media player and a decoder factory to decode the given media file before playing. If we see the code of decoder factory we will notice that there is a problem with the code, as audio and video decoders are mixed in the DecoderFactory.java..

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