Editing Strategy pattern (section)

=== UML class and sequence diagram ===
[[File:w3sDesign Strategy Design Pattern UML.jpg|frame|none|A sample UML class and sequence diagram for the Strategy design pattern.<ref>{{cite web|title=The Strategy design pattern - Structure and Collaboration|url=http://w3sdesign.com/?gr=b09&ugr=struct|website=w3sDesign.com|access-date=2017-08-12}}</ref>]]
In the above [[Unified Modeling Language|UML]] [[class diagram]], the <code>Context</code> class does not implement an algorithm directly.
Instead, <code>Context</code> refers to the <code>Strategy</code> interface for performing an algorithm (<code>strategy.algorithm()</code>), which makes <code>Context</code> independent of how an algorithm is implemented.
The <code>Strategy1</code> and <code>Strategy2</code> classes implement the <code>Strategy</code> interface, that is, implement (encapsulate) an algorithm.
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The [[Unified Modeling Language|UML]] [[sequence diagram]]
shows the runtime interactions: The <code>Context</code> object delegates an algorithm to different <code>Strategy</code> objects. First, <code>Context</code> calls <code>algorithm()</code> on a <code>Strategy1</code> object,
which performs the algorithm and returns the result to <code>Context</code>. 
Thereafter, <code>Context</code> changes its strategy and calls <code>algorithm()</code> on a <code>Strategy2</code> object,
which performs the algorithm and returns the result to <code>Context</code>.