Strategy Pattern

• Pluggable strategy for layout management
• Layout manager object responsible for executing concrete strategy
• Generalizes to Strategy Design Pattern
• Other manifestation: Comparators
  

  Comparator comp = new CountryComparatorByName();
  Collections.sort(countries, comp);
  

Strategy Pattern

Context

1. A class can benefit from different variants for an algorithm
2. Clients sometimes want to replace standard algorithms with custom versions

Solution

1. Define an interface type that is an abstraction for the algorithm
2. Actual strategy classes realize this interface type.
3. Clients can supply strategy objects
4. Whenever the algorithm needs to be executed, the context class calls the appropriate methods of the strategy object
   

Strategy Pattern

Strategy Pattern: Layout Management     

Strategy Pattern: Sorting

Maintained by John Loomis, last updated 25 February 2007