Alternative renderer for Jericho HTML Parser

UrlMappedRenderer.java

/*
Copyright (c) 2015 Michiel Hendriks

This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not
   claim that you wrote the original software. If you use this software
   in a product, an acknowledgment in the product documentation would be
   appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
   misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
package net.htmlparser.jericho;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;

public class UrlMappedRenderer extends Renderer {

	private Map<String, Integer> urlMap;

	public UrlMappedRenderer(final Segment segment) {
		super(segment);
	}

	public String renderHyperlinkURL(final StartTag startTag) {
		final String href = startTag.getAttributeValue("href");
		if (href == null || href.startsWith("javascript:")) {
			return null;
		}
		try {
			URI uri = new URI(href);
			if (!uri.isAbsolute()) {
				return null;
			}
		} catch (URISyntaxException ex) {
			return null;
		}
		if (urlMap == null) {
			urlMap = new LinkedHashMap<String, Integer>();
		}
		if (!urlMap.containsKey(href)) {
			urlMap.put(href, Integer.valueOf(urlMap.size() + 1));
		}
		return String.format("[%d]", urlMap.get(href));
	}

	public void appendTo(final Appendable appendable) throws IOException {
		super.appendTo(appendable);
		printUrlMap(appendable);
		urlMap = null;
	}

	private void printUrlMap(final Appendable appendable) throws IOException {
		if (urlMap == null || urlMap.isEmpty()) {
			return;
		}
		appendable.append(getNewLine());
		appendable.append(getNewLine());
		final int digitLength = Integer.toString(urlMap.size()).length();
		final String fmtString = "  %" + digitLength + "d. ";
		for (Entry<String, Integer> entry : urlMap.entrySet()) {
			appendable.append(String.format(fmtString, entry.getValue()));
			appendable.append(entry.getKey());
			appendable.append(getNewLine());
		}
	}
}

Instead of adding the URL right after the content where it was linked it created references like [1] which are printed at the end of the content.
Links with the same URL get the same reference.

Attached zlib license