Patterns - 002: Basic java patterns

BASIC PATTERNS

In general, the functionality of an object-oriented system is encapsulated in the form of a set of objects. These objects provide different services either on their own or by interacting with other objects. In other words, a given object may rely upon the services offered by a different object to provide the service it is designed for. An object that requests a service from another object is referred as a client object. Some other objects in the system may seek the services offered by the client object.

Pattern Name	Description
Interface	Can be used to design a set of service provider classes that offer the same service so that a client object can use different classes of service provider objects in a seamless manner without having to alter the client implementation.
Abstract Parent Class	Useful for designing a framework for the consistent implementation of the functionality common to a set of related classes.
Private Methods	Provide a way of designing a class behavior so that external objects are not permitted to access the behavior that is meant only for the internal use.
Accessor Methods	Provide a way of accessing an object’s state using specific methods. This approach discourages different client objects from directly accessing the attributes of an object, resulting in a more maintainable class structure.
Constant Data Manager	Useful for designing an easy to maintain, centralized repository for the constant data in an application.
Immutable Object	Used to ensure that the state of an object cannot be changed. May be used to ensure that the concurrent access to a data object by several client objects does not result in race conditions.
Monitor	A way of designing an application object so that it does not produce unpredictable results when more than one thread tries to access the object at the same time in a multithreaded environment.