Eclipse Platform
Release 3.6

org.eclipse.equinox.p2.query
Class Collector<T>

java.lang.Object
  extended by org.eclipse.equinox.p2.query.Collector<T>
Type Parameters:
T - The type of object accepted by this collector
All Implemented Interfaces:
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 Summary
static Collector<?> EMPTY_COLLECTOR
           
 
Constructor Summary
Collector()
          Creates a new collector.
 
Method Summary
 boolean accept(T object)
          Accepts an object.
 void addAll(IQueryResult<T> queryResult)
          Adds the elements from one collector to this collector
static
<T> Collector<T>
emptyCollector()
           
protected  Collection<T> getCollection()
          Returns the collection that is being used to collect results.
 boolean isEmpty()
          Returns whether this collector is empty.
 Iterator<T> iterator()
          Returns an iterator on the collected objects.
 IQueryResult<T> query(IQuery<T> query, IProgressMonitor monitor)
          Performs a query on this results of this collector.
 int size()
          Returns the number of collected objects.
 T[] toArray(Class<T> clazz)
          Returns the collected objects as an array
 Set<T> toSet()
          Returns a copy of the collected objects.
 Set<T> toUnmodifiableSet()
          Returns the collected objects as an immutable collection.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

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>
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

Eclipse Platform
Release 3.6

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