ObjectPool.java

/**
 * Copyright (c) 2007-2011, OpenMaLi Project Group all rights reserved.
 * 
 * Portions based on the Sun's javax.vecmath interface, Copyright by Sun
 * Microsystems or Kenji Hiranabe's alternative GC-cheap implementation.
 * Many thanks to the developers.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 * 
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * 
 * Neither the name of the 'OpenMaLi Project Group' nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) A
 * RISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE
 */
package org.openmali.pooling;

import java.util.ArrayList;
import java.util.List;

/**
 * Simple collection used to store free objects which we need to work with
 * frequently. This is to solve some of the issues with garbage collection of
 * frequently used objects
 * 
 * @param <T>
 * 
 * @author David Yazel
 * @author Marvin Froehlich (aka Qudus)
 */
public abstract class ObjectPool<T>
{
    private final List<T> objects;
    private int n;
    
    public int getSize()
    {
        return ( n );
    }
    
    /**
     * Creates a new instance of a pooled object.
     * 
     * @return the new object instance
     */
    protected abstract T newInstance();
    
    public T alloc()
    {
        if ( n > 0 )
        {
            T o = objects.remove( --n );
            
            return ( o );
        }
        
        return ( newInstance() );
    }
    
    public void free( T o )
    {
        if ( o == null )
            return;
        
        objects.add( o );
        n++;
    }
    
    public ObjectPool( int initialSize )
    {
        this.objects = new ArrayList<T>( initialSize );
        this.n = 0;
    }
}