[Java] Annotation Type Sortable

A class annotation used to make a class Comparable by multiple Comparators. As an example, given this class:

 @Sortable class Person {
     String first
     String last
     Integer born
 }
 

The generated Groovy class will:

• implement the Comparable interface
• have a compareTo method based on the first, last and born properties (priority ordering will be according to the ordering of property definition, highest first, unless 'includes' is used; in which case, priority will be according to the order given in the includes list)
• have three Comparator methods named comparatorByFirst, comparatorByLast and comparatorByBorn

The properties within the class must themselves be Comparable or @Sortable.

More examples:

 //--------------------------------------------------------------------------
 import groovy.transform.Sortable
 import groovy.transform.ToString

 @Sortable
 @ToString
 class Course {
     // Order of properties determines priority when sorting
     String title
     Date beginDate
     Integer maxAttendees  // int doesn't implement Comparable, so use Integer
 }


 final Course groovy = new Course(
         title: 'Groovy', beginDate: new Date() + 7, maxAttendees: 40)
 final Course groovy2 = new Course(
         title: 'Groovy', beginDate: new Date() + 2, maxAttendees: 50)
 final Course grails = new Course(
         title: 'Grails', beginDate: new Date() + 1, maxAttendees: 20)


 final List<Course> courses = [groovy, groovy2, grails]
 assert courses.last().title == 'Grails'

 // Use toSorted() method to sort
 final List<Course> sorted = courses.toSorted()

 assert sorted.first().title == 'Grails'
 assert sorted.last().title == 'Groovy'
 assert sorted.maxAttendees == [20, 50, 40]
 

 //--------------------------------------------------------------------------
 // Order of fields for includes determines priority when sorting
 import groovy.transform.Sortable
 import groovy.transform.ToString

 @Sortable(includes = ['title', 'maxAttendees'])
 // Or @Sortable(excludes = ['beginDate'])
 @ToString
 class Course {
     String title
     Date beginDate
     Integer maxAttendees
 }

 final Course groovy = new Course(
         title: 'Groovy', beginDate: new Date() + 7, maxAttendees: 40)
 final Course groovy2 = new Course(
         title: 'Groovy', beginDate: new Date() + 2, maxAttendees: 50)
 final Course grails = new Course(
         title: 'Grails', beginDate: new Date() + 1, maxAttendees: 20)


 final List<Course> courses = [groovy, groovy2, grails]

 // Use toSorted() method to sort
 final List<Course> sorted = courses.toSorted()

 assert sorted.first().title == 'Grails'
 assert sorted.last().title == 'Groovy'
 assert sorted.maxAttendees == [20, 40, 50]

 //--------------------------------------------------------------------------
 // Static methods to create comparators.
 final Comparator byMaxAttendees = Course.comparatorByMaxAttendees()
 final List<Course> sortedByMaxAttendees = courses.sort(false, byMaxAttendees)

 assert sortedByMaxAttendees.maxAttendees == [20, 40, 50]
 // beginDate is not used for sorting
 assert sortedByMaxAttendees[2].beginDate < sortedByMaxAttendees[1].beginDate

 assert Course.declaredMethods.name.findAll { it.startsWith('comparatorBy') }.toSorted() == ['comparatorByMaxAttendees', 'comparatorByTitle']
 

Authors:

Andres Almiray

Paul King