ArrayEnumeration.java Source code

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Here is the source code for ArrayEnumeration.java

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/**
 * The utillib library.
 * More information is available at http://www.jinchess.com/.
 * Copyright (C) 2002 Alexander Maryanovsky.
 * All rights reserved.
 *
 * The utillib 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.
 *
 * The utillib 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 utillib library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

import java.util.Enumeration;
import java.util.NoSuchElementException;

/**
 * An implementation of the Enumeration interface which enumerates the items of
 * an array. Note: This class is not thread safe.
 */

public class ArrayEnumeration implements Enumeration {

    /**
     * The array.
     */

    private Object[] arr;

    /**
     * The index of the first enumerated item.
     */

    private final int offset;

    /**
     * The amount of the enumerated items.
     */

    private final int count;

    /**
     * The index of the next returned item.
     */

    private int curIndex;

    /**
     * Creates a new ArrayEnumeration which enumerates the items of the given
     * array. The first <code>count</code> items starting at index 
     * <code>offset</code> are enumerated.
     *
     * @throws IllegalArgumentException if the offset and/or count parameters are
     * invalid.
     */

    public ArrayEnumeration(Object[] arr, int offset, int count) {
        if ((offset < 0) || (offset + count > arr.length) || (count < 0))
            throw new IllegalArgumentException("Invalid enumeration range");

        this.arr = new Object[arr.length];
        System.arraycopy(arr, 0, this.arr, 0, arr.length);
        this.offset = offset;
        this.count = count;

        curIndex = offset;
    }

    /**
     * Creates a new ArrayEnumeration which enumerates all the items of the given
     * array.
     */

    public ArrayEnumeration(Object[] arr) {
        this(arr, 0, arr.length);
    }

    /**
     * Returns the next element in the enumeration.
     */

    public Object nextElement() {
        if (!hasMoreElements())
            throw new NoSuchElementException();

        Object item = arr[curIndex];
        arr[curIndex++] = null; // We don't want to keep a reference to it any longer than we have to.
        if (!hasMoreElements())
            arr = null; // Neither do we need this any more.
        return item;
    }

    /**
     * Returns true if there are more elements in the enumeration.
     */

    public boolean hasMoreElements() {
        return curIndex < offset + count;
    }

}