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Showing posts from August, 2009

Measures of confusion with JSR-275

I love the idea behind JSR-275, a units of measurement API for Java (see here for a background article by Jean-Marie Dautelle, the lead author) but I wish there were more examples out there about how to use it properly.

I'm presently writing some code for a spatial simulation. I want the user to be able to specify constraints on spatial entities such as their maximum area, width, movement over time and so forth. Bringing JSR-275 to bear on this means that I can use a consistent set of units within the code while leaving the user free to express their input data in whatever units are convenient for them.

The theory is beautiful but my, alas, my code is ugly.

Take this snippet for example...
// get a constraint from the user
Constraint constraint = ...

// get the unit used internally for this constraint (e.g. "m")
Unit<?> stdUnit = ...

// the value for the constraint (in the user's units)
double value = constraint.getValue();

// get the label for the user's units (e.…