Package org.eclipse.equinox.p2.query

Class Collector<T>

  • Type Parameters:
    T - The type of object accepted by this collector
    All Implemented Interfaces:
    Iterable<T>, IQueryable<T>, IQueryResult<T>
    public class Collector<T>
extends Object
implements IQueryResult<T>
    A collector is a generic visitor that collects objects passed to it, and can then express the result of the visit in various forms. The collector can also short-circuit a traversal by returning false from its accept(Object) method.

    This default collector just accepts all objects passed to it. Clients may subclass to perform different processing on the objects passed to it.

    Since:
    2.0

    • Field Detail

      • EMPTY_COLLECTOR

        public static final Collector<?> EMPTY_COLLECTOR

    • Constructor Detail

      • Collector

        public Collector()
        Creates a new collector.

    • Method Detail

      • emptyCollector

        public static final <T> Collector<T> emptyCollector()

      • accept

        public boolean accept​(T object)
        Accepts an object.

        This default implementation adds the objects to a list. Clients may override this method to perform additional filtering, add different objects to the list, short-circuit the traversal, or process the objects directly without collecting them.

        Parameters:
        object - the object to collect or visit
        Returns:
        true if the traversal should continue, or false to indicate the traversal should stop.

      • addAll

        public void addAll​(IQueryResult<T> queryResult)
        Adds the elements from one collector to this collector
        Parameters:
        queryResult - The collector from which the elements should be retrieved

      • getCollection

        protected Collection<T> getCollection()
        Returns the collection that is being used to collect results. Unlike toSet(), this returns the actual modifiable collection that is being used to store results. The return value is only intended to be used within subclasses and should not be exposed outside of a collection class.
        Returns:
        the collection being used to collect results.

      • isEmpty

        public boolean isEmpty()
        Returns whether this collector is empty.
        Specified by:
        isEmpty in interface IQueryResult<T>
        Returns:
        true if this collector has accepted any results, and false otherwise.

      • iterator

        public Iterator<T> iterator()
        Returns an iterator on the collected objects.
        Specified by:
        iterator in interface IQueryResult<T>
        Specified by:
        iterator in interface Iterable<T>
        Returns:
        an iterator of the collected objects.

      • size

        public int size()
        Returns the number of collected objects.

      • toArray

        public T[] toArray​(Class<T> clazz)
        Returns the collected objects as an array
        Specified by:
        toArray in interface IQueryResult<T>
        Parameters:
        clazz - The type of array to return
        Returns:
        The array of results
        Throws:
        ArrayStoreException - the runtime type of the specified array is not a super-type of the runtime type of every collected object

      • toSet

        public Set<T> toSet()
        Returns a copy of the collected objects.
        Specified by:
        toSet in interface IQueryResult<T>
        Returns:
        An unmodifiable collection of the collected objects

      • query

        public IQueryResult<T> query​(IQuery<T> query,
                             IProgressMonitor monitor)
        Performs a query on this results of this collector.
        Specified by:
        query in interface IQueryable<T>
        Parameters:
        query - The query to perform
        monitor - a progress monitor, or null if progress reporting is not desired
        Returns:
        The collector argument

      • toUnmodifiableSet

        public Set<T> toUnmodifiableSet()
        Returns the collected objects as an immutable collection.
        Specified by:
        toUnmodifiableSet in interface IQueryResult<T>
        Returns:
        An unmodifiable collection of the collected objects