Annotation Interface MonotonicQualifier

@Documented @Retention(RUNTIME) @Target(ANNOTATION_TYPE) public @interface MonotonicQualifier
A meta-annotation that indicates that a qualifier indicates that an expression goes monotonically from a type qualifier T to another qualifier S. The annotation S is called the target of the monotonic qualifier, and has to be indicated by value().

This meta-annotation can be used on the declaration of the monotonic qualifier used for the type-system at hand, and is often called MonoT if the target is T. The subtyping hierarchy has to be defined as follows:

 T <: MonoT <: S
where <: indicates the subtyping relation.

An expression of a monotonic type can only be assigned expressions of the target type T. This means that an expression of the monotonic type MonoT cannot be assigned to a variable of the same type.

Reading an expression of a monotonic type MonoT might always yield an expression of type S. However, once it has been observed that a variable has the target type T, the monotonic property ensures that it will stay of type T for the rest of the program execution. This is even true if arbitrary other code is executed.

Note that variables of a monotonic type can be re-assigned arbitrarily often, but only with expressions of the target type.

  • Required Element Summary

    Required Elements
    Modifier and Type
    Required Element
    Class<? extends Annotation>