Package: groovy.transform

## [Java] Annotation Type Sortable

- groovy.transform.Sortable

-     @Retention(RetentionPolicy.RUNTIME)
      @Target({ElementType.TYPE})
      @GroovyASTTransformationClass("org.codehaus.groovy.transform.SortableASTTransformation")
      public @interface Sortable

  A class annotation used to make a class Comparable by (potentially) 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`
  - sort by natural order by default, reversed natural order can be specified
  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']

       //--------------------------------------------------------------------------
       // Sorting by max attendees using reversed order
       import groovy.transform.Sortable
       import groovy.transform.ToString

       @Sortable(includes = ['points'], reversed = true)
       @ToString
       class LeaderBoardEntry {
           String team
           int points
       }

       final LeaderBoardEntry teamA = new LeaderBoardEntry(team: "Team A", points: 30)
       final LeaderBoardEntry teamB = new LeaderBoardEntry(team: "Team B", points: 80)
       final LeaderBoardEntry teamC = new LeaderBoardEntry(team: "Team C", points: 50)

       final List<LeaderBoardEntry> leaderBoard = [teamA, teamB, teamC].toSorted()

       assert leaderBoard.first().team == 'Team B'
       assert leaderBoard.last().team == 'Team A'
       assert leaderBoard.points == [80, 50, 30]

- - ### Element Summary

    Optional Element Summary
    Type | Name and Description
    --- | ---
    `boolean` | `allNames` Whether to include all fields and/or properties in the comparison algorithm, including those with names that are considered internal.
    `boolean` | `allProperties` Whether to include all properties (as per the JavaBean spec) in the comparison algorithm.
    `String[]` | `excludes` Property names to exclude in the comparison algorithm.
    `boolean` | `includeSuperProperties` Whether to include super properties in the comparison algorithm.
    `String[]` | `includes` Property names to include in the comparison algorithm.
    `boolean` | `reversed` Set to true so that comparator uses reversed natural order.

  - ### Inherited Methods Summary

    Inherited Methods
    Methods inherited from class | Name
    --- | ---
    `class Object` | `wait, wait, wait, equals, toString, hashCode, getClass, notify, notifyAll`

- - ### Element Detail

    - #### public boolean allNames

      Whether to include all fields and/or properties in the comparison algorithm, including those with names that are considered internal.

      Since:
        2.5.2
      Default:
        false

    - #### public boolean allProperties

      Whether to include all properties (as per the JavaBean spec) in the comparison algorithm. Groovy recognizes any field-like definitions with no explicit visibility as property definitions and always includes them in the comparison algorithm. Groovy also treats any explicitly created getXxx() or isYyy() methods as property getters as per the JavaBean specification. Set this flag to false explicitly exclude such properties. JavaBean properties come after any Groovy properties for a given class (unless 'includes' is used to determine the order).

      Since:
        2.5.2
      Default:
        true

    - #### public String[] excludes

      Property names to exclude in the comparison algorithm. Must not be used if 'includes' is used.

      Default:
        {}

    - #### public boolean includeSuperProperties

      Whether to include super properties in the comparison algorithm. Groovy properties and potentially JavaBean properties (in that order) from superclasses come before the members from a subclass (unless 'includes' is used to determine the order).

      Since:
        2.5.2
      Default:
        false

    - #### public String[] includes

      Property names to include in the comparison algorithm. Must not be used if 'excludes' is used. The default value is a special marker value indicating that no includes are defined; all properties are included if 'includes' remains undefined and 'excludes' is explicitly or implicitly an empty list.

      Default:
        { Undefined.STRING }

    - #### public boolean reversed

      Set to true so that comparator uses reversed natural order.

      Since:
        2.5.0
      Default:
        false