// This Source Code is in the Public Domain per: http://litesoft.org/License.txt
package org.litesoft.core.util;

import java.util.*;

/**
 * An Iterator that implements the Null Object pattern.<p>
 * <p/>
 * This class is not directly instantiable as it is implemented with the
 * singleton pattern.<p>
 * <p/>
 * This class <i>fully</i> implements the java.util.Iterator interface, but
 * always indicates that there are no more elements.<p>
 *
 * @author George Smith
 * @version 1.0 7/28/01
 */

public final class NullIterator<T> extends AbstractReadOnlyIterator<T>
{
    /**
     * Get the single instance of the Iterator.<p>
     *
     * @return the NullIterator instance.
     */
    @SuppressWarnings({"unchecked"})
    public static <V> Iterator<V> getInstance()
    {
        return (Iterator<V>) INSTANCE;
    }

    private static final Iterator INSTANCE = new NullIterator();

    private NullIterator()
    {
    }

    /**
     * Returns <tt>false</tt>, because there is <b>never</b> another element.<p>
     * <p/>
     * Note: <tt>next</tt> will throw an exception.<p>
     *
     * @return <tt>false</tt>.<p>
     *
     * @see <a href="http://java.sun.com/j2se/1.3/docs/api/java/lang/Util/Iterator.html#hasNext()">java.util.Iterator#hasNext()</a>
     * @see AbstractReadOnlyIterator#next()
     */
    @Override
    public boolean hasNext()
    {
        return false;
    }

    /**
     * Returns a debug/human friendly String that represents this.<p>
     *
     * @return A String representation of this.
     */
    @Override
    public String toString()
    {
        return "NullIterator";
    }
}