com.mchange.v2.coalesce.CoalescerFactory Maven / Gradle / Ivy
/*
* Distributed as part of mchange-commons-java 0.2.6.3
*
* Copyright (C) 2013 Machinery For Change, Inc.
*
* Author: Steve Waldman
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of EITHER:
*
* 1) The GNU Lesser General Public License (LGPL), version 2.1, as
* published by the Free Software Foundation
*
* OR
*
* 2) The Eclipse Public License (EPL), version 1.0
*
* You may choose which license to accept if you wish to redistribute
* or modify this work. You may offer derivatives of this work
* under the license you have chosen, or you may provide the same
* choice of license which you have been offered here.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*
* You should have received copies of both LGPL v2.1 and EPL v1.0
* along with this software; see the files LICENSE-EPL and LICENSE-LGPL.
* If not, the text of these licenses are currently available at
*
* LGPL v2.1: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
* EPL v1.0: http://www.eclipse.org/org/documents/epl-v10.php
*
*/
package com.mchange.v2.coalesce;
public final class CoalescerFactory
{
/**
* Creates a "Coalescer" that coalesces Objects according to their
* equals() method. Given a set of n Objects among whom equals() would
* return true, calling coalescer.coalesce() in any order on any sequence
* of these Objects will always return a single "canonical" instance.
*
* This method creates a weak, synchronized coalesecer, safe for use
* by multiple Threads.
*/
public static Coalescer createCoalescer()
{ return createCoalescer( true, true ); }
/**
* Creates a "Coalescer" that coalesces Objects according to their
* equals() method. Given a set of n Objects among whom equals() would
* return true, calling coalescer.coalesce() in any order on any sequence
* of these Objects will always return a single "canonical" instance.
*
* @param weak if true, the Coalescer will use WeakReferences to hold
* its canonical instances, allowing them to be garbage
* collected if they are nowhere in use.
*
* @param synced if true, access to the Coalescer will be automatically
* synchronized. if set to false, then users must manually
* synchronize access.
*/
public static Coalescer createCoalescer( boolean weak, boolean synced )
{ return createCoalescer( null, weak, synced ); }
/**
* Creates a "Coalescer" that coalesces Objects according to the
* checkCoalesce() method of a "CoalesceChecker". Given a set of
* n Objects among whom calling cc.checkCoalesce() on any pair would
* return true, calling coalescer.coalesce() in any order on any sequence
* of these Objects will always return a single "canonical" instance.
* This allows one to define immutable value Objects whose equals()
* method is a mere identity test -- one can use a Coalescer in a
* factory method to ensure that no two instances with the same values
* are made available to clients.
*
* @param cc CoalesceChecker that will be used to determine whether two
* objects are equivalent and can be coalesced. [If cc is null, then two
* objects will be coalesced iff o1.equals( o2 ).]
*
* @param weak if true, the Coalescer will use WeakReferences to hold
* its canonical instances, allowing them to be garbage
* collected if they are nowhere in use.
*
* @param synced if true, access to the Coalescer will be automatically
* synchronized. if set to false, then users must manually
* synchronize access.
*/
public static Coalescer createCoalescer( CoalesceChecker cc, boolean weak, boolean synced )
{
Coalescer out;
if ( cc == null )
{
out = ( weak ?
(Coalescer) new WeakEqualsCoalescer() :
(Coalescer) new StrongEqualsCoalescer() );
}
else
{
out = ( weak ?
(Coalescer) new WeakCcCoalescer( cc ) :
(Coalescer) new StrongCcCoalescer( cc ) );
}
return ( synced ? new SyncedCoalescer( out ) : out );
}
}