IteratorUtils.java Source code

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Here is the source code for IteratorUtils.java

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/*
 * Distributed as part of debuggen v.0.1.0
 *
 * Copyright (C) 2005 Machinery For Change, Inc.
 *
 * Author: Steve Waldman <swaldman@mchange.com>
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 2.1, as 
 * published by the Free Software Foundation.
 *
 * This software 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 software; see the file LICENSE.  If not, write to the
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 */

import java.util.*;
import java.lang.reflect.Array;

public final class IteratorUtils {
    public final static Iterator EMPTY_ITERATOR = new Iterator() {
        public boolean hasNext() {
            return false;
        }

        public Object next() {
            throw new NoSuchElementException();
        }

        public void remove() {
            throw new IllegalStateException();
        }
    };

    public static Iterator oneElementUnmodifiableIterator(final Object elem) {
        return new Iterator() {
            boolean shot = false;

            public boolean hasNext() {
                return (!shot);
            }

            public Object next() {
                if (shot)
                    throw new NoSuchElementException();
                else {
                    shot = true;
                    return elem;
                }
            }

            public void remove() {
                throw new UnsupportedOperationException("remove() not supported.");
            }
        };
    }

    public static boolean equivalent(Iterator ii, Iterator jj) {
        while (true) {
            boolean ii_hasnext = ii.hasNext();
            boolean jj_hasnext = jj.hasNext();
            if (ii_hasnext ^ jj_hasnext)
                return false;
            else if (ii_hasnext) {
                Object iiNext = ii.next();
                Object jjNext = jj.next();
                if (iiNext == jjNext)
                    continue;
                else if (iiNext == null)
                    return false;
                else if (!iiNext.equals(jjNext))
                    return false;
            } else
                return true;
        }
    }

    public static ArrayList toArrayList(Iterator ii, int initial_capacity) {
        ArrayList out = new ArrayList(initial_capacity);
        while (ii.hasNext())
            out.add(ii.next());
        return out;
    }

    /**
     * Fills an array with the contents of an iterator. If the array is too small,
     * it will contain the first portion of the iterator. If the array can contain
     * more elements than the iterator, extra elements are left untouched, unless
     * null_terminate is set to true, in which case the element immediately following
     * the last from the iterator is set to null. (This method is intended to make
     * it easy to implement Collection.toArray(Object[] oo) methods...
     *
     * @param null_terminate iff there is extra space in the array, set the element
     *        immediately after the last from the iterator to null.
     */
    public static void fillArray(Iterator ii, Object[] fillMe, boolean null_terminate) {
        int i = 0;
        int len = fillMe.length;
        while (i < len && ii.hasNext())
            fillMe[i++] = ii.next();
        if (null_terminate && i < len)
            fillMe[i] = null;
    }

    public static void fillArray(Iterator ii, Object[] fillMe) {
        fillArray(ii, fillMe, false);
    }

    /**
     * @param null_terminate iff there is extra space in the array, set the element
     *        immediately after the last from the iterator to null.
     */
    public static Object[] toArray(Iterator ii, int array_size, Class componentClass, boolean null_terminate) {
        Object[] out = (Object[]) Array.newInstance(componentClass, array_size);
        fillArray(ii, out, null_terminate);
        return out;
    }

    public static Object[] toArray(Iterator ii, int array_size, Class componentClass) {
        return toArray(ii, array_size, componentClass, false);
    }

    /**
     * Designed to help implement Collection.toArray(Object[] )methods... does
     * the right thing if you can express an iterator and know the size of your
     * Collection.
     */
    public static Object[] toArray(Iterator ii, int ii_size, Object[] maybeFillMe) {
        if (maybeFillMe.length >= ii_size) {
            fillArray(ii, maybeFillMe, true);
            return maybeFillMe;
        } else {
            Class componentType = maybeFillMe.getClass().getComponentType();
            return toArray(ii, ii_size, componentType);
        }
    }

    private IteratorUtils() {
    }
}