abstract-factory strategy log4net
Strategy pattern
The Strategy pattern encapsulates alternative algorithms (or strategies) for a particular task. It allows a method to be swapped out at runtime by any other method (strategy) without the client realizing it. Essentially, Strategy is a group of algorithms that are interchangeable.
Say we like to test the performance of different sorting algorithms to an array of numbers: shell sort, heap sort, bubble sort, quicksort, etc. Applying the Strategy pattern to these algorithms allows the test program to loop through all algorithms, simply by changing them at runtime and test each of these against the array. For Strategy to work all method signatures must be the same so that they can vary without the client program knowing about it.
Strategy dofactory – link
Class code: strategy demo in JAVA!
Abstract factory pattern
An Abstract Factory creates objects that are related by a common theme. In object-oriented programming a Factory is an object that creates other objects. An Abstract Factory has abstracted out a theme which is shared by the newly created objects.
Suppose we have two Abstract Factories whose task it is to create page controls, such as, buttons, textboxes, radio buttons, and listboxes. One is the Light Factory which creates controls that are white and the other the Dark Factory which creates controls that are black. Both Factories creates the same types of controls, but they differ in color, which is their common theme. This is an implementation of the Abstract Factory pattern.
This includes scenarios in which the creation process involves object caching, sharing or re-using of objects, complex logic, or applications that maintain object and type counts, and objects that interact with different resources or devices. If your application needs more control over the object creation process, consider using a Factory.
Abstract factory dofactory – link
Class code: abs factory demo in JAVA!
Apache log4net
log4net is a tool to help the programmer output log statements to a variety of output targets. In case of problems with an application, it is helpful to enable logging so that the problem can be located. With log4net it is possible to enable logging at runtime without modifying the application binary. The log4net package is designed so that log statements can remain in production code without incurring a high performance cost. It follows that the speed of logging (or rather not logging) is crucial.
At the same time, log output can be so voluminous that it quickly becomes overwhelming. One of the distinctive features of log4net (and common to all of the log4x libraries) is the notion of hierarchical loggers. Using these loggers it is possible to selectively control which log statements are output at arbitrary granularity.
Apache log4net – home site!
Log4net appenders list
Log4net – demo project
Log4net – stackify demo!
Nice interview question
formula: “AA,ABC@BC,DD@CDA”….
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More topics covered:
- choosing strategy based on input
- changing strategy at run-time
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