PropertiesIterator.java Source code

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Here is the source code for PropertiesIterator.java

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/**
 * 
 * JFreeReport : a free Java reporting library
 * 
 *
 * Project Info:  http://reporting.pentaho.org/
 *
 * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
 *
 * 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 2.1 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.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
 * in the United States and other countries.]
 *
 * ------------
 * PropertiesIterator.java
 * ------------
 * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
 */

import java.util.Iterator;
import java.util.Properties;

/**
 * The properties iterator iterates over a set of enumerated properties. The
 * properties are named by an optional prefix plus a number, which is counted up
 * on each iteration: <p/>
 * <ul>
 * <li>prefix_0 </li>
 * <li>prefix_1 </li>
 * <li>prefix_2 </li>
 * <li>... </li>
 * </ul>
 * <p/> The iterator iterates over all subsequent numbered proprties until the
 * number-sequence is finished.
 * 
 * @author Thomas Morgner
 * 
 */
public class PropertiesIterator implements Iterator {
    /**
     * The underlying properties collection.
     */
    private Properties properties;

    /**
     * The property name prefix.
     */
    private String prefix;

    /**
     * An incremental counter.
     */
    private int count;

    /**
     * Creates a new properties iterator without an prefix.
     * 
     * @param properties
     *          the underlying properties collection.
     */
    public PropertiesIterator(final Properties properties) {
        this(properties, null);
    }

    /**
     * Creates a new properties iterator with the given prefix.
     * 
     * @param properties
     *          the underlying properties collection.
     * @param prefix
     *          a prefix for generating property names (null permitted).
     */
    public PropertiesIterator(final Properties properties, final String prefix) {
        if (properties == null) {
            throw new NullPointerException();
        }
        this.properties = properties;
        this.prefix = prefix;
        this.count = 0;
    }

    /**
     * Returns true if there is a property in the underlying collection with a
     * name that matches the name returned by the getNextKey() method.
     * 
     * @return true if there is another property with a name in the correct form.
     */
    public boolean hasNext() {
        return properties.containsKey(getNextKey());
    }

    /**
     * Generates a property name in the form <prefix>
     * &lt;count&gt;.
     * 
     *  The &lt;count&gt; begins at 0,
     *  and is automatically incremented with each call to the next() method.
     * 
     *  @return the next key in the sequence
     * 
     */
    private String getNextKey() {
        if (prefix == null) {
            return String.valueOf(count);
        }
        return prefix + String.valueOf(count);
    }

    /**
     * Returns the property with a name the same as the name generated by the
     * getNextKey() method, or null if there is no such property (that is, then
     * end of the sequence has been reached).
     * 
     * @return the property or null.
     */
    public Object next() {
        final String value = properties.getProperty(getNextKey());
        count++;
        return value;
    }

    /**
     * Always throws UnsupportedOperationException as remove is not implemented
     * for this iterator.
     * 
     * @throws UnsupportedOperationException
     *           as remove is not supported.
     */
    public void remove() {
        throw new UnsupportedOperationException();
    }

}