org.checkerframework.checker.units.qual

Annotation Type PolyUnit

@Documented
 @Retention(value=RUNTIME)
 @Target(value={TYPE_USE,TYPE_PARAMETER})
 @PolymorphicQualifier(value=UnknownUnits.class)
public @interface PolyUnit

A polymorphic qualifier for the units-of-measure type system implemented by the Units Checker.

Any method written using @PolyUnit conceptually has many versions: in each one, every instance of @PolyUnit has been replaced by a different unit qualifier such as @kg (kilograms) or @h (hours).

The following example shows how method triplePolyUnit can be used to process either meters or seconds:

  @PolyUnit int triplePolyUnit(@PolyUnit int amount) {
    return 3*amount;
  }

  void testPolyUnit() {
    @m int m1 = 7 * UnitsTools.m;
    @m int m2 = triplePolyUnit(m1);

    @s int sec1 = 7 * UnitsTools.s;
    @s int sec2 = triplePolyUnit(sec1);

    // :: error: (assignment.type.incompatible)
    @s int sec3 = triplePolyUnit(m1);
  }
 

See the Checker Framework Manual:

Units Checker, Qualifier polymorphism