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/*
 * Copyright (c) 1998-2007, Peter T Mount

 * All rights reserved.
 *
 * 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 retep.org.uk 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) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package uk.org.retep.util.builder.impl;

import javax.annotation.Nullable;
import uk.org.retep.util.builder.LastBuilder;

/**
 * Implementation of the {@link LastBuilder} interface
 * @param  Type of subclass
 * @param  Type of object being built
 * @author peter
 */
public abstract class AbstractLastBuilder
        extends AbstractBuilder
        implements LastBuilder
{

    private D lastBuild;

    /**
     * {@inheritDoc}
     */
    @Override
    @Nullable
    public final D getLastBuild()
    {
        return lastBuild;
    }

    /**
     * Subclasses should call this before performing any actual build.
     * This resets lastBuild to null, so when a {@link #build()} fails then
     * {@link #getLastBuild()} will return null as no valid object is available.
     */
    protected final void resetLastBuild()
    {
        lastBuild = null;
    }

    /**
     * Subclasses must call this just prior to returning the build object.
     * It sets the return value of {@link #getLastBuild()}
     *
     * @param lastBuild The built object returned by {@link #build()}
     * @return lastBuild
     */
    protected final D setLastBuild( @Nullable final D lastBuild )
    {
        this.lastBuild = lastBuild;
        return lastBuild;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public final D buildIfNeeded()
    {
        if( lastBuild == null )
        {
            build();
        }
        return lastBuild;
    }
}