mergedclauseiterator.java

来自「Mandarax是一个规则引擎的纯Java实现。它支持多类型的事实和基于反映的规」· Java 代码 · 共 94 行

/*
 * Copyright (C) 1999-2004 <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</a>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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 library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package org.mandarax.util;


import org.mandarax.kernel.Clause;
import org.mandarax.kernel.ClauseSetException;

/**
 * Iterator for clauses. This iterator simple merges other iterators:
 * it first iterates the first iterator, then the second iterator, and so on.
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 * @since 1.2
 */
public final class MergedClauseIterator extends AbstractClauseIterator {

    private ClauseIterator[] slaves     = null;
    private int              index      = 0;
    private Clause           nextClause = null;

    /**
     * Constructor.
     * @param iterators an array of clause iterators
     */
    public MergedClauseIterator(ClauseIterator[] iterators) {
        super ();

        slaves = iterators;
    }

    /**
     * Constructor.
     * @param iterators a collection of clause iterators
     */
    public MergedClauseIterator(java.util.Collection iterators) {
        super ();

        Object objs = iterators.toArray ();

        slaves = new ClauseIterator[iterators.size ()];

        System.arraycopy (objs, 0, slaves, 0, iterators.size ());
    }

    /**
     * Indicates whether there is a next clause.
     * @return boolean
     * @throws ClauseSetException
     */
    public boolean hasMoreClauses() throws ClauseSetException {
        nextClause = null;

        if((index < slaves.length) && (index > -1)) {
            if(slaves[index].hasMoreClauses ()) {
                nextClause = slaves[index].nextClause ();

                return true;
            } else {

                // go to next slave     
                index = index + 1;

                return hasMoreClauses ();
            }
        }

        return false;
    }

    /**
     * Return the next clause.
     * @return the next clause.
     */
    public Clause nextClause() {
        return nextClause;
    }
}