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JFreeChart is a class library, written in Java, for generating charts. Utilising the Java2D API, it supports a wide range of chart types including bar charts, pie charts, line charts, XY-plots, time series plots, Sankey charts and more.

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/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-present, by David Gilbert and Contributors.
 *
 * Project Info:  http://www.jfree.org/jfreechart/index.html
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA.
 *
 * [Oracle and Java are registered trademarks of Oracle and/or its affiliates. 
 * Other names may be trademarks of their respective owners.]
 *
 * ----------------
 * RootHandler.java
 * ----------------
 * (C) Copyright 2003-present, by David Gilbert and Contributors.
 *
 * Original Author:  David Gilbert;
 * Contributor(s):   -;
 *
 */

package org.jfree.data.xml;

import java.util.Stack;

import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * A SAX handler that delegates work to sub-handlers.
 */
public class RootHandler extends DefaultHandler implements DatasetTags {

    /** The sub-handlers. */
    private Stack subHandlers;

    /**
     * Creates a new handler.
     */
    public RootHandler() {
        this.subHandlers = new Stack();
    }

    /**
     * Returns the stack of sub handlers.
     *
     * @return The sub-handler stack.
     */
    public Stack getSubHandlers() {
        return this.subHandlers;
    }

    /**
     * Receives some (or all) of the text in the current element.
     *
     * @param ch  character buffer.
     * @param start  the start index.
     * @param length  the length of the valid character data.
     *
     * @throws SAXException for errors.
     */
    @Override
    public void characters(char[] ch, int start, int length)
        throws SAXException {
        DefaultHandler handler = getCurrentHandler();
        if (handler != this) {
            handler.characters(ch, start, length);
        }
    }

    /**
     * Returns the handler at the top of the stack.
     *
     * @return The handler.
     */
    public DefaultHandler getCurrentHandler() {
        DefaultHandler result = this;
        if (this.subHandlers != null) {
            if (this.subHandlers.size() > 0) {
                Object top = this.subHandlers.peek();
                if (top != null) {
                    result = (DefaultHandler) top;
                }
            }
        }
        return result;
    }

    /**
     * Pushes a sub-handler onto the stack.
     *
     * @param subhandler  the sub-handler.
     */
    public void pushSubHandler(DefaultHandler subhandler) {
        this.subHandlers.push(subhandler);
    }

    /**
     * Pops a sub-handler from the stack.
     *
     * @return The sub-handler.
     */
    public DefaultHandler popSubHandler() {
        return (DefaultHandler) this.subHandlers.pop();
    }

}