Mithil Shah

The Observer pattern is such a popular design pattern that the jdk has provided a set of classes that make it easy to implement it. Here’s how we define the pattern : An Observer pattern allows multiple objects to “observe” or “listen to” the changes in one object. To explain the Observer pattern lets use … Read more

In the earlier tutorials we have seen the factory method and the abstract factory pattern. In this tutorial we look at another creational pattern called the Builder Design pattern. The Builder Design pattern specifies a builder class that creates multiple objects in a step by step manner. The client uses the builder to build the … Read more

The Composite Design pattern is a structural pattern that defines a way to access a group of objects through a single object. It can be though of as a tree structure where a node holds reference to its children. The main actors in these pattern are Node The Node defines an interface that each object … Read more

What is Facade Pattern The Facade pattern is a structural pattern that provides an entry point to a subsystem of classes. It provides a simpler interface to one or more interfaces. The salient points of a facade pattern are : A facade hides the complexity of a subsystem by providing an interface that is easy … Read more

Decorator Design pattern provides a way to add additional functionality to an object without modifying it. The additional functionality is added to the object at runtime and it does not require extending the class. Decorators have the same interface as the object they are decorating. Their purpose is to provide additional features at runtime and … Read more

What is Adapter Design Pattern The Adapter Design pattern is use when a client expects interfaceA but is provided with interfaceB. The adapter maps the methods from interfaceB to interfaceA. This pattern is used when the client expects certain methods in an interface or class(adaptee) but the adaptee does not provide those methods (Note that … Read more

This is the last of the creational patterns. In the earlier tutorials we have seen the factory method, the abstract factory pattern, the builder pattern and the prototype pattern. In this tutorial we will look at the Singleton pattern. The singleton pattern ensures that only once instance of a class is created and the client … Read more

What is the Prototype Design Pattern The prototype design pattern is a method where a new instance of an object is obtained by asking a manager to return the clone of one. In the earlier tutorials we saw how abstract factory pattern can be used to create a family of objects and builder pattern can … Read more

Abstract factory pattern is a creational pattern. It provides an interface using which a client can instantiate a group of related Objects. This tutorial explains the Abstract factory pattern using a Car manufacturing algorithm. Example We design a framework that can build cars. We build two types of cars, a Mazda and a Ferrari. The … Read more