Question

I am implementing a few strategies (Strategy Pattern) which have some common behavior and am undecided where the common operations should live.

• Assuming I 1 context and 3 strategies, some of the operations used in the strategies are shared, some are needed only by 2 others just be 1 of the strategies.
• There is no member level state shared, therefore the only operations are effectively stateless.
• The intention of the operations are to support the formatting of state to a file, like a view helper.

Option 1: Make an AbstractStrategy class

• I’m using Java so this immediately
  takes away using this feature in the
  future.
• Inheritance tends to result.
  in a ridge structure.
• Operations would be final.

Option 2: Create a Util class of static helpers

• Flexible, but feels like a code smell for some reason.
• Not ridged.

Any recommendations or preferences?

Note the level I am working at is the Strategy level, not the Context level (see wikipedia link).

Answer 1

There is one reason… one huge reason… to use a static Util class over an abstract class or interface.

So you can add more methods at a later date.

With an abstract class or interface, any change you make to that class/interface has to be changed in all classes that inherit from it. This is especially problematic if you’re writing a public API.

The Java framework has util classes with static methods scattered throughout. The most well known ones are in the java.util package: Collections and Arrays.