Priority.java

/**
 * OpenSpotLight - Open Source IT Governance Platform
 *
 * Copyright (c) 2009, CARAVELATECH CONSULTORIA E TECNOLOGIA EM INFORMATICA LTDA
 * or third-party contributors as indicated by the @author tags or express
 * copyright attribution statements applied by the authors.  All third-party
 * contributions are distributed under license by CARAVELATECH CONSULTORIA E
 * TECNOLOGIA EM INFORMATICA LTDA.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program 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.
 *
 * See the GNU Lesser General Public License  for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 *
 ***********************************************************************
 * OpenSpotLight - Plataforma de Governança de TI de Código Aberto
 *
 * Direitos Autorais Reservados (c) 2009, CARAVELATECH CONSULTORIA E TECNOLOGIA
 * EM INFORMATICA LTDA ou como contribuidores terceiros indicados pela etiqueta
 * @author ou por expressa atribuição de direito autoral declarada e atribuída pelo autor.
 * Todas as contribuições de terceiros estão distribuídas sob licença da
 * CARAVELATECH CONSULTORIA E TECNOLOGIA EM INFORMATICA LTDA.
 *
 * Este programa é software livre; você pode redistribuí-lo e/ou modificá-lo sob os
 * termos da Licença Pública Geral Menor do GNU conforme publicada pela Free Software
 * Foundation.
 *
 * Este programa é distribuído na expectativa de que seja útil, porém, SEM NENHUMA
 * GARANTIA; nem mesmo a garantia implícita de COMERCIABILIDADE OU ADEQUAÇÃO A UMA
 * FINALIDADE ESPECÍFICA. Consulte a Licença Pública Geral Menor do GNU para mais detalhes.
 *
 * Você deve ter recebido uma cópia da Licença Pública Geral Menor do GNU junto com este
 * programa; se não, escreva para:
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 */

package org.openspotlight.common.concurrent;

import org.openspotlight.common.util.Assertions;
import org.openspotlight.common.util.HashCodes;

/**
 * Class to be used as a hierarchy to priorities. One example is under thread pool task executor. Imagine that a processor
 * executes tasks with priorities. It will execute first the task one, and after task two, and so on. Sometimes should be good to
 * execute task 2.1 before task 3 and after task 2. This behavior can be achieved here by instantiating a
 * {@link Priority#createPriority(int...)} passing 2,1 as a parameter.
 * 
 * @author feu
 */
public final class Priority implements Comparable<Priority> {

    private final int      hashcode;

    private final int      priorityNumber;

    private final Priority subPriority;

    private Priority(
                      final int priorityNumber, final Priority subPriority) {
        Assertions.checkCondition("positiveValue", priorityNumber > 0);
        this.priorityNumber = priorityNumber;
        this.subPriority = subPriority;
        hashcode = HashCodes.hashOf(priorityNumber, subPriority != null ? subPriority.hashcode : 0);
    }

    public static Priority createPriority(final int... priorities) {
        Assertions.checkNotNull("priorities", priorities);
        Assertions.checkCondition("prioritiesNotEmpty", priorities.length > 0);
        Priority parent = null;
        for (int i = priorities.length; i != 0; i--) {
            parent = new Priority(priorities[i - 1], parent);
        }
        return parent;
    }

    private int compareIntValues(final int thisVal,
                                  final int thatVal) {
        return thisVal < thatVal ? -1 : thisVal == thatVal ? 0 : 1;

    }

    @Override
    public int compareTo(final Priority o) {
        Priority thisPriority = this;
        Priority thatPriority = o;
        while (true) {
            final int thisVal = thisPriority != null ? thisPriority.priorityNumber : 0;
            final int thatVal = thatPriority != null ? thatPriority.priorityNumber : 0;
            final int result = compareIntValues(thisVal, thatVal);
            if (result != 0) { return result; }
            thisPriority = thisPriority.subPriority;
            thatPriority = thatPriority.subPriority;
            if (thisPriority == null && thatPriority == null) { return 0; }
            if (thisPriority == null || thatPriority == null) {
                if (thisPriority == null) { return compareIntValues(1, 0); }
                return compareIntValues(0, 1);
            }
        }
    }

    @Override
    public boolean equals(final Object o) {
        if (!(o instanceof Priority)) { return false; }
        return compareTo((Priority) o) == 0;
    }

    @Override
    public int hashCode() {
        return hashcode;
    }

}