Optional (Gradle API 2.14.1)

org.gradle.api.tasks

## Annotation Type Optional

-     @Documented
      @Retention(value=RUNTIME)
      @Target(value={METHOD,FIELD,PARAMETER})
      public @interface Optional

  Marks a task property as optional. This means that a value does not have to be specified for the property, but any value specified must meet the validation constraints for the property.

  This annotation can be used with any of the following property annotations:

  - `Input`
  - `InputFile`
  - `InputDirectory`
  - `InputFiles`
  - `OutputFile`
  - `OutputDirectory`