HSQLDB example source code file (WrapperIterator.java)

This example HSQLDB source code file (WrapperIterator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - HSQLDB tags/keywords

iterator, iterator, nosuchelementexception, nosuchelementexception, object, object, util, wrapperiterator, wrapperiterator

The HSQLDB WrapperIterator.java source code

/* Copyright (c) 2001-2008, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


package org.hsqldb.lib;

import java.util.NoSuchElementException;

/**
 *  An Iterator that returns the elements of a specified array, or other
 *  iterators etc. The collection of objects returned depends on the
 *  constructor used.<p>
 *
 *  Based on similar Enumerator code by boucherb@users
 *
 * @author fred@users
 * @version 1.9.0
 * @since HSQLDB 1.7.2
 */
public class WrapperIterator implements Iterator {

    private static final Object[] emptyelements = new Object[0];
    private Object[]              elements;
    private int                   i;

    // chained iterators
    private boolean  chained;
    private Iterator it1;
    private Iterator it2;

    /** return only not null elements */
    private boolean notNull;

    /**
     * Constructor for an empty iterator. <p>
     */
    public WrapperIterator() {
        this.elements = emptyelements;
    }

    /**
     * Constructor for all elements of the specified array. <p>
     *
     * @param elements the array of objects to enumerate
     */
    public WrapperIterator(Object[] elements) {
        this.elements = elements;
    }

    /**
     * Constructor for not-null elements of specified array. <p>
     *
     * @param elements the array of objects to iterate
     */
    public WrapperIterator(Object[] elements, boolean notNull) {
        this.elements = elements;
        this.notNull  = notNull;
    }

    /**
     * Constructor for a singleton object iterator
     *
     * @param element the single object to iterate
     */
    public WrapperIterator(Object element) {
        this.elements = new Object[]{ element };
    }

    /**
     * Constructor for a chained iterator that returns the elements of the two
     * specified iterators.
     */
    public WrapperIterator(Iterator it1, Iterator it2) {

        this.it1 = it1;
        this.it2 = it2;
        chained  = true;
    }

    /**
     * Tests if this iterator contains more elements. <p>
     *
     * @return  <code>true if this iterator contains more elements;
     *          <code>false otherwise.
     */
    public boolean hasNext() {

        // for chained iterators
        if (chained) {
            if (it1 == null) {
                if (it2 == null) {
                    return false;
                }

                if (it2.hasNext()) {
                    return true;
                }

                it2 = null;

                return false;
            } else {
                if (it1.hasNext()) {
                    return true;
                }

                it1 = null;

                return hasNext();
            }
        }

        // for other interators
        if (elements == null) {
            return false;
        }

        for (; notNull && i < elements.length && elements[i] == null; i++) {}

        if (i < elements.length) {
            return true;
        } else {

            // release elements for garbage collection
            elements = null;

            return false;
        }
    }

    /**
     * Returns the next element.
     *
     * @return the next element
     * @throws NoSuchElementException if there is no next element
     */
    public Object next() {

        // for chained iterators
        if (chained) {
            if (it1 == null) {
                if (it2 == null) {
                    throw new NoSuchElementException();
                }

                if (it2.hasNext()) {
                    return it2.next();
                }

                it2 = null;

                next();
            } else {
                if (it1.hasNext()) {
                    return it1.next();
                }

                it1 = null;

                next();
            }
        }

        // for other itertors
        if (hasNext()) {
            return elements[i++];
        }

        throw new NoSuchElementException();
    }

    public int nextInt() {
        throw new NoSuchElementException();
    }

    public long nextLong() {
        throw new NoSuchElementException();
    }

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

    public void setValue(Object value) {
        throw new NoSuchElementException();
    }
}