termiterator.java

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则

/*
 * 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.Term;

/**
 * Iterator for terms. The iterator provides a simple mean for
 * iterating but avoiding casting as it is the case when using
 * the <code>java.util.Enumeration</code> or <code>java.util.Iterator</code>
 * interface. But both interfaces are also supported.
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 * @since 1.0
 */
public final class TermIterator
        implements java.util.Enumeration, java.util.Iterator {

    private Term[] terms  = null;
    private int    cursor = 0;

    /**
     * Constructor.
     * @param t an array of terms
     */
    public TermIterator(Term[] t) {
        super ();

        terms = t;
    }

    /**
     * Constructor. Pass the initial cursor.
     * @param t an array of terms
     * @param c the initial value of the cursor
     */
    private TermIterator(Term[] t, int c) {
        super ();

        terms  = t;
        cursor = c;
    }

    /**
     * Indicates whether there are more elements.
     * Duplicates the functionality of <code>hasMoreTerms()</code> in order to implement
     * the <code>java.util.Enumeration</code> interface.
     * @return true if there are more elements, false otherwise
     */
    public boolean hasMoreElements() {
        return hasMoreTerms ();
    }

    /**
     * Indicates whether there are more terms.
     * @return true if there are more elements, false otherwise
     */
    public boolean hasMoreTerms() {
        return cursor < terms.length;
    }

    /**
     * Indicates whether there are more elements.
     * Duplicates the functionality of <code>hasMoreTerms()</code> in order to implement
     * the <code>java.util.Iterator</code> interface.
     * @return true if there are more elements, false otherwise
     */
    public boolean hasNext() {
        return hasMoreTerms ();
    }

    /**
     * Get the next element.
     * Duplicates the functionality of <code>nextTerm()</code> in order to implement
     * the <code>java.util.Iterator</code> interface.
     * @return the next term
     */
    public Object next() {
        return nextTerm ();
    }

    /**
     * Get the next term.
     * Duplicates the functionality of <code>nextTerm()</code> in order to implement
     * the <code>java.util.Enumeration</code> interface.
     * @return the next term
     */
    public Object nextElement() {
        return nextTerm ();
    }

    /**
     * Get the next term.
     * @return the next term
     */
    public Term nextTerm() {
        int i = cursor;

        cursor = cursor + 1;

        return terms[i];
    }

    /**
     * Remove an element. Not supported, throws a <code>UnsupportedOperationException</code>.
     */
    public void remove() {
        throw new UnsupportedOperationException ();
    }
}