diff --git a/src/main/java/com/redfin/sitemapgenerator/AbstractSitemapGeneratorOptions.java b/src/main/java/com/redfin/sitemapgenerator/AbstractSitemapGeneratorOptions.java
index 8521113..871493f 100644
--- a/src/main/java/com/redfin/sitemapgenerator/AbstractSitemapGeneratorOptions.java
+++ b/src/main/java/com/redfin/sitemapgenerator/AbstractSitemapGeneratorOptions.java
@@ -16,12 +16,15 @@ abstract class AbstractSitemapGeneratorOptions<THIS extends AbstractSitemapGener
 	boolean gzip = false;
 	
 	public AbstractSitemapGeneratorOptions(URL baseUrl, File baseDir) {
-		if (baseDir == null) throw new NullPointerException("baseDir may not be null");
 		if (baseUrl == null) throw new NullPointerException("baseUrl may not be null");
 		this.baseDir = baseDir;
 		this.baseUrl = baseUrl.toString();
 	}
 	
+	public AbstractSitemapGeneratorOptions(URL baseUrl) {
+		this(baseUrl, null);
+	}
+	
 	/** The prefix of the name of the sitemaps we'll create; by default this is "sitemap" */
 	public THIS fileNamePrefix(String fileNamePrefix) {
 		if (fileNamePrefix == null) throw new NullPointerException("fileNamePrefix may not be null");
diff --git a/src/main/java/com/redfin/sitemapgenerator/AbstractSitemapUrlRenderer.java b/src/main/java/com/redfin/sitemapgenerator/AbstractSitemapUrlRenderer.java
index 8f45216..fd794f6 100644
--- a/src/main/java/com/redfin/sitemapgenerator/AbstractSitemapUrlRenderer.java
+++ b/src/main/java/com/redfin/sitemapgenerator/AbstractSitemapUrlRenderer.java
@@ -1,33 +1,31 @@
 package com.redfin.sitemapgenerator;
 
-import java.io.IOException;
-import java.io.OutputStreamWriter;
-
 abstract class AbstractSitemapUrlRenderer<T extends WebSitemapUrl> implements ISitemapUrlRenderer<T> {
-
-	public void render(WebSitemapUrl url, OutputStreamWriter out, W3CDateFormat dateFormat, String additionalData)
-			throws IOException {
-		out.write("  <url>\n");
-		out.write("    <loc>");
-		out.write(url.getUrl().toString());
-		out.write("</loc>\n");
+	
+	public void render(WebSitemapUrl url, StringBuilder sb, W3CDateFormat dateFormat, String additionalData) {
+		sb.append("  <url>\n");
+		sb.append("    <loc>");
+		sb.append(url.getUrl().toString());
+		sb.append("</loc>\n");
 		if (url.getLastMod() != null) {
-			out.write("    <lastmod>");
-			out.write(dateFormat.format(url.getLastMod()));
-			out.write("</lastmod>\n");
+			sb.append("    <lastmod>");
+			sb.append(dateFormat.format(url.getLastMod()));
+			sb.append("</lastmod>\n");
 		}
 		if (url.getChangeFreq() != null) {
-			out.write("    <changefreq>");
-			out.write(url.getChangeFreq().toString());
-			out.write("</changefreq>\n");
+			sb.append("    <changefreq>");
+			sb.append(url.getChangeFreq().toString());
+			sb.append("</changefreq>\n");
 		}
 		if (url.getPriority() != null) {
-			out.write("    <priority>");
-			out.write(url.getPriority().toString());
-			out.write("</priority>\n");
+			sb.append("    <priority>");
+			sb.append(url.getPriority().toString());
+			sb.append("</priority>\n");
 		}
-		if (additionalData != null) out.write(additionalData);
-		out.write("  </url>\n");
+		if (additionalData != null) {
+			sb.append(additionalData);
+		}
+		sb.append("  </url>\n");
 	}
 
 	public void renderTag(StringBuilder sb, String namespace, String tagName, Object value) {
diff --git a/src/main/java/com/redfin/sitemapgenerator/GoogleCodeSitemapGenerator.java b/src/main/java/com/redfin/sitemapgenerator/GoogleCodeSitemapGenerator.java
index db0df6f..06fe971 100644
--- a/src/main/java/com/redfin/sitemapgenerator/GoogleCodeSitemapGenerator.java
+++ b/src/main/java/com/redfin/sitemapgenerator/GoogleCodeSitemapGenerator.java
@@ -1,8 +1,6 @@
 package com.redfin.sitemapgenerator;
 
 import java.io.File;
-import java.io.IOException;
-import java.io.OutputStreamWriter;
 import java.net.MalformedURLException;
 import java.net.URL;
 
@@ -37,6 +35,26 @@ public class GoogleCodeSitemapGenerator extends SitemapGenerator<GoogleCodeSitem
 		this(new SitemapGeneratorOptions(baseUrl, baseDir));
 	}
 	
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public GoogleCodeSitemapGenerator(String baseUrl) throws MalformedURLException {
+		this(new SitemapGeneratorOptions(new URL(baseUrl)));
+	}
+	
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public GoogleCodeSitemapGenerator(URL baseUrl) {
+		this(new SitemapGeneratorOptions(baseUrl));
+	}
+	
 	/** Configures a builder so you can specify sitemap generator options
 	 * 
 	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
@@ -63,23 +81,23 @@ public class GoogleCodeSitemapGenerator extends SitemapGenerator<GoogleCodeSitem
 		public Class<GoogleCodeSitemapUrl> getUrlClass() {
 			return GoogleCodeSitemapUrl.class;
 		}
-
-		public void render(GoogleCodeSitemapUrl url, OutputStreamWriter out,
-				W3CDateFormat dateFormat) throws IOException {
-			StringBuilder sb = new StringBuilder();
-			sb.append("    <codesearch:codesearch>\n");
-			renderTag(sb, "codesearch", "filetype", url.getFileType());
-			renderTag(sb, "codesearch", "license", url.getLicense());
-			renderTag(sb, "codesearch", "filename", url.getFileName());
-			renderTag(sb, "codesearch", "packageurl", url.getPackageUrl());
-			renderTag(sb, "codesearch", "packagemap", url.getPackageMap());
-			sb.append("    </codesearch:codesearch>\n");
-			super.render(url, out, dateFormat, sb.toString());
-		}
 		
 		public String getXmlNamespaces() {
 			return "xmlns:codesearch=\"http://www.google.com/codesearch/schemas/sitemap/1.0\"";
 		}
+
+		public void render(GoogleCodeSitemapUrl url, StringBuilder sb,
+				W3CDateFormat dateFormat) {
+			StringBuilder tagSb = new StringBuilder();
+			tagSb.append("    <codesearch:codesearch>\n");
+			renderTag(tagSb, "codesearch", "filetype", url.getFileType());
+			renderTag(tagSb, "codesearch", "license", url.getLicense());
+			renderTag(tagSb, "codesearch", "filename", url.getFileName());
+			renderTag(tagSb, "codesearch", "packageurl", url.getPackageUrl());
+			renderTag(tagSb, "codesearch", "packagemap", url.getPackageMap());
+			tagSb.append("    </codesearch:codesearch>\n");
+			super.render(url, sb, dateFormat, tagSb.toString());
+		}
 		
 	}
 
diff --git a/src/main/java/com/redfin/sitemapgenerator/GoogleGeoSitemapGenerator.java b/src/main/java/com/redfin/sitemapgenerator/GoogleGeoSitemapGenerator.java
index a0546cc..6c9a8a6 100644
--- a/src/main/java/com/redfin/sitemapgenerator/GoogleGeoSitemapGenerator.java
+++ b/src/main/java/com/redfin/sitemapgenerator/GoogleGeoSitemapGenerator.java
@@ -1,8 +1,6 @@
 package com.redfin.sitemapgenerator;
 
 import java.io.File;
-import java.io.IOException;
-import java.io.OutputStreamWriter;
 import java.net.MalformedURLException;
 import java.net.URL;
 
@@ -57,6 +55,27 @@ public class GoogleGeoSitemapGenerator extends SitemapGenerator<GoogleGeoSitemap
 	public GoogleGeoSitemapGenerator(URL baseUrl, File baseDir) {
 		this(new SitemapGeneratorOptions(baseUrl, baseDir));
 	}
+	
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public GoogleGeoSitemapGenerator(String baseUrl) throws MalformedURLException {
+		this(new SitemapGeneratorOptions(new URL(baseUrl)));
+	}
+	
+	
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public GoogleGeoSitemapGenerator(URL baseUrl) {
+		this(new SitemapGeneratorOptions(baseUrl));
+	}
 
 	private static class Renderer extends AbstractSitemapUrlRenderer<GoogleGeoSitemapUrl> implements ISitemapUrlRenderer<GoogleGeoSitemapUrl> {
 
@@ -64,19 +83,17 @@ public class GoogleGeoSitemapGenerator extends SitemapGenerator<GoogleGeoSitemap
 			return GoogleGeoSitemapUrl.class;
 		}
 
-		public void render(GoogleGeoSitemapUrl url, OutputStreamWriter out,
-				W3CDateFormat dateFormat) throws IOException {
-			StringBuilder sb = new StringBuilder();
-			sb.append("    <geo:geo>\n");
-			sb.append("      <geo:format>"+url.getFormat()+"</geo:format>\n");
-			sb.append("    </geo:geo>\n");
-			super.render(url, out, dateFormat, sb.toString());
-			
-		}
-
 		public String getXmlNamespaces() {
 			return "xmlns:geo=\"http://www.google.com/geo/schemas/sitemap/1.0\"";
 		}
+
+		public void render(GoogleGeoSitemapUrl url, StringBuilder sb, W3CDateFormat dateFormat) {
+			StringBuilder tagSb = new StringBuilder();
+			tagSb.append("    <geo:geo>\n");
+			tagSb.append("      <geo:format>"+url.getFormat()+"</geo:format>\n");
+			tagSb.append("    </geo:geo>\n");
+			super.render(url, sb, dateFormat, tagSb.toString());
+		}
 		
 	}
 }
diff --git a/src/main/java/com/redfin/sitemapgenerator/GoogleMobileSitemapGenerator.java b/src/main/java/com/redfin/sitemapgenerator/GoogleMobileSitemapGenerator.java
index 12a349b..6bdd1d6 100644
--- a/src/main/java/com/redfin/sitemapgenerator/GoogleMobileSitemapGenerator.java
+++ b/src/main/java/com/redfin/sitemapgenerator/GoogleMobileSitemapGenerator.java
@@ -1,8 +1,6 @@
 package com.redfin.sitemapgenerator;
 
 import java.io.File;
-import java.io.IOException;
-import java.io.OutputStreamWriter;
 import java.net.MalformedURLException;
 import java.net.URL;
 
@@ -56,6 +54,26 @@ public class GoogleMobileSitemapGenerator extends SitemapGenerator<GoogleMobileS
 	public GoogleMobileSitemapGenerator(URL baseUrl, File baseDir) {
 		this(new SitemapGeneratorOptions(baseUrl, baseDir));
 	}
+	
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public GoogleMobileSitemapGenerator(String baseUrl) throws MalformedURLException {
+		this(new SitemapGeneratorOptions(new URL(baseUrl)));
+	}
+	
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public GoogleMobileSitemapGenerator(URL baseUrl) {
+		this(new SitemapGeneratorOptions(baseUrl));
+	}
 
 	private static class Renderer extends AbstractSitemapUrlRenderer<GoogleMobileSitemapUrl> implements ISitemapUrlRenderer<GoogleMobileSitemapUrl> {
 
@@ -63,16 +81,14 @@ public class GoogleMobileSitemapGenerator extends SitemapGenerator<GoogleMobileS
 			return GoogleMobileSitemapUrl.class;
 		}
 
-		public void render(GoogleMobileSitemapUrl url, OutputStreamWriter out,
-				W3CDateFormat dateFormat) throws IOException {
-			String additionalData = "    <mobile:mobile/>\n";
-			super.render(url, out, dateFormat, additionalData);
-			
-		}
-
 		public String getXmlNamespaces() {
 			return "xmlns:mobile=\"http://www.google.com/schemas/sitemap-mobile/1.0\"";
 		}
+
+		public void render(GoogleMobileSitemapUrl url, StringBuilder sb, W3CDateFormat dateFormat) {
+			String additionalData = "    <mobile:mobile/>\n";
+			super.render(url, sb, dateFormat, additionalData);
+		}
 		
 	}
 }
diff --git a/src/main/java/com/redfin/sitemapgenerator/GoogleNewsSitemapGenerator.java b/src/main/java/com/redfin/sitemapgenerator/GoogleNewsSitemapGenerator.java
index 2cf038e..6e88f3b 100644
--- a/src/main/java/com/redfin/sitemapgenerator/GoogleNewsSitemapGenerator.java
+++ b/src/main/java/com/redfin/sitemapgenerator/GoogleNewsSitemapGenerator.java
@@ -1,8 +1,6 @@
 package com.redfin.sitemapgenerator;
 
 import java.io.File;
-import java.io.IOException;
-import java.io.OutputStreamWriter;
 import java.net.MalformedURLException;
 import java.net.URL;
 
@@ -69,26 +67,44 @@ public class GoogleNewsSitemapGenerator extends SitemapGenerator<GoogleNewsSitem
 		this(new SitemapGeneratorOptions(baseUrl, baseDir));
 	}
 
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public GoogleNewsSitemapGenerator(String baseUrl) throws MalformedURLException {
+		this(new SitemapGeneratorOptions(new URL(baseUrl)));
+	}
+	
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public GoogleNewsSitemapGenerator(URL baseUrl) {
+		this(new SitemapGeneratorOptions(baseUrl));
+	}
+	
 	private static class Renderer extends AbstractSitemapUrlRenderer<GoogleNewsSitemapUrl> implements ISitemapUrlRenderer<GoogleNewsSitemapUrl> {
 
 		public Class<GoogleNewsSitemapUrl> getUrlClass() {
 			return GoogleNewsSitemapUrl.class;
 		}
 
-		public void render(GoogleNewsSitemapUrl url, OutputStreamWriter out,
-				W3CDateFormat dateFormat) throws IOException {
-			StringBuilder sb = new StringBuilder();
-			sb.append("    <news:news>\n");
-			renderTag(sb, "news", "publication_date", dateFormat.format(url.getPublicationDate()));
-			renderTag(sb, "news", "keywords", url.getKeywords());
-			sb.append("    </news:news>\n");
-			super.render(url, out, dateFormat, sb.toString());
-			
-		}
-
 		public String getXmlNamespaces() {
 			return "xmlns:news=\"http://www.google.com/schemas/sitemap-news/0.9\"";
 		}
+
+		public void render(GoogleNewsSitemapUrl url, StringBuilder sb, W3CDateFormat dateFormat) {
+			StringBuilder tagSb = new StringBuilder();
+			tagSb.append("    <news:news>\n");
+			renderTag(tagSb, "news", "publication_date", dateFormat.format(url.getPublicationDate()));
+			renderTag(tagSb, "news", "keywords", url.getKeywords());
+			tagSb.append("    </news:news>\n");
+			super.render(url, sb, dateFormat, tagSb.toString());
+		}
 		
 	}
 
diff --git a/src/main/java/com/redfin/sitemapgenerator/GoogleVideoSitemapGenerator.java b/src/main/java/com/redfin/sitemapgenerator/GoogleVideoSitemapGenerator.java
index 1cbf8e4..64f9301 100644
--- a/src/main/java/com/redfin/sitemapgenerator/GoogleVideoSitemapGenerator.java
+++ b/src/main/java/com/redfin/sitemapgenerator/GoogleVideoSitemapGenerator.java
@@ -1,8 +1,6 @@
 package com.redfin.sitemapgenerator;
 
 import java.io.File;
-import java.io.IOException;
-import java.io.OutputStreamWriter;
 import java.net.MalformedURLException;
 import java.net.URL;
 
@@ -56,49 +54,67 @@ public class GoogleVideoSitemapGenerator extends SitemapGenerator<GoogleVideoSit
 	public GoogleVideoSitemapGenerator(URL baseUrl, File baseDir) {
 		this(new SitemapGeneratorOptions(baseUrl, baseDir));
 	}
+	
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public GoogleVideoSitemapGenerator(String baseUrl) throws MalformedURLException {
+		this(new SitemapGeneratorOptions(new URL(baseUrl)));
+	}
+	
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public GoogleVideoSitemapGenerator(URL baseUrl) {
+		this(new SitemapGeneratorOptions(baseUrl));
+	}
 
 	private static class Renderer extends AbstractSitemapUrlRenderer<GoogleVideoSitemapUrl> implements ISitemapUrlRenderer<GoogleVideoSitemapUrl> {
 
 		public Class<GoogleVideoSitemapUrl> getUrlClass() {
 			return GoogleVideoSitemapUrl.class;
 		}
-
-		public void render(GoogleVideoSitemapUrl url, OutputStreamWriter out,
-				W3CDateFormat dateFormat) throws IOException {
-			StringBuilder sb = new StringBuilder();
-			sb.append("    <video:video>\n");
-			renderTag(sb, "video", "content_loc", url.getContentUrl());
-			if (url.getPlayerUrl() != null) {
-				sb.append("      <video:player_loc allow_embed=\"");
-				sb.append(url.getAllowEmbed());
-				sb.append("\">");
-				sb.append(url.getPlayerUrl());
-				sb.append("</video:player_loc>\n");
-			}
-			renderTag(sb, "video", "thumbnail_loc", url.getThumbnailUrl());
-			renderTag(sb, "video", "title", url.getTitle());
-			renderTag(sb, "video", "description", url.getDescription());
-			renderTag(sb, "video", "rating", url.getRating());
-			renderTag(sb, "video", "view_count", url.getViewCount());
-			if (url.getPublicationDate() != null) {
-				renderTag(sb, "video", "publication_date", dateFormat.format(url.getPublicationDate()));
-			}
-			if (url.getTags() != null) {
-				for (String tag : url.getTags()) {
-					renderTag(sb, "video", "tag", tag);
-				}
-			}
-			renderTag(sb, "video", "category", url.getCategory());
-			renderTag(sb, "video", "family_friendly", url.getFamilyFriendly());
-			renderTag(sb, "video", "duration", url.getDurationInSeconds());
-			sb.append("    </video:video>\n");
-			super.render(url, out, dateFormat, sb.toString());
-			
-		}
 		
 		public String getXmlNamespaces() {
 			return "xmlns:video=\"http://www.google.com/schemas/sitemap-video/1.1\"";
 		}
+
+		public void render(GoogleVideoSitemapUrl url, StringBuilder sb, W3CDateFormat dateFormat) {
+			StringBuilder tagSb = new StringBuilder();
+			tagSb.append("    <video:video>\n");
+			renderTag(tagSb, "video", "content_loc", url.getContentUrl());
+			if (url.getPlayerUrl() != null) {
+				tagSb.append("      <video:player_loc allow_embed=\"");
+				tagSb.append(url.getAllowEmbed());
+				tagSb.append("\">");
+				tagSb.append(url.getPlayerUrl());
+				tagSb.append("</video:player_loc>\n");
+			}
+			renderTag(tagSb, "video", "thumbnail_loc", url.getThumbnailUrl());
+			renderTag(tagSb, "video", "title", url.getTitle());
+			renderTag(tagSb, "video", "description", url.getDescription());
+			renderTag(tagSb, "video", "rating", url.getRating());
+			renderTag(tagSb, "video", "view_count", url.getViewCount());
+			if (url.getPublicationDate() != null) {
+				renderTag(tagSb, "video", "publication_date", dateFormat.format(url.getPublicationDate()));
+			}
+			if (url.getTags() != null) {
+				for (String tag : url.getTags()) {
+					renderTag(tagSb, "video", "tag", tag);
+				}
+			}
+			renderTag(tagSb, "video", "category", url.getCategory());
+			renderTag(tagSb, "video", "family_friendly", url.getFamilyFriendly());
+			renderTag(tagSb, "video", "duration", url.getDurationInSeconds());
+			tagSb.append("    </video:video>\n");
+			super.render(url, sb, dateFormat, tagSb.toString());
+		}
 		
 	}
 	
diff --git a/src/main/java/com/redfin/sitemapgenerator/ISitemapUrlRenderer.java b/src/main/java/com/redfin/sitemapgenerator/ISitemapUrlRenderer.java
index 3c421fd..2839e52 100644
--- a/src/main/java/com/redfin/sitemapgenerator/ISitemapUrlRenderer.java
+++ b/src/main/java/com/redfin/sitemapgenerator/ISitemapUrlRenderer.java
@@ -1,11 +1,8 @@
 package com.redfin.sitemapgenerator;
 
-import java.io.IOException;
-import java.io.OutputStreamWriter;
-
 interface ISitemapUrlRenderer<T extends ISitemapUrl> {
 	
 	public Class<T> getUrlClass();
 	public String getXmlNamespaces();
-	public void render(T url, OutputStreamWriter out, W3CDateFormat dateFormat) throws IOException;
+	public void render(T url, StringBuilder sb, W3CDateFormat dateFormat);
 }
diff --git a/src/main/java/com/redfin/sitemapgenerator/SitemapGenerator.java b/src/main/java/com/redfin/sitemapgenerator/SitemapGenerator.java
index b88e066..265b1e9 100644
--- a/src/main/java/com/redfin/sitemapgenerator/SitemapGenerator.java
+++ b/src/main/java/com/redfin/sitemapgenerator/SitemapGenerator.java
@@ -59,10 +59,12 @@ abstract class SitemapGenerator<U extends ISitemapUrl, THIS extends SitemapGener
 		UrlUtils.checkUrl(url.getUrl().toString(), baseUrl);
 		if (urls.size() == maxUrls) {
 			if (!allowMultipleSitemaps) throw new RuntimeException("More than " + maxUrls + " urls, but allowMultipleSitemaps is false.  Enable allowMultipleSitemaps to split the sitemap into multiple files with a sitemap index.");
-			if (mapCount == 0) mapCount++;
-			writeSiteMap();
-			mapCount++;
-			urls.clear();
+			if (baseDir != null) {
+				if (mapCount == 0) mapCount++;
+				writeSiteMap();
+				mapCount++;
+				urls.clear();
+			}
 		}
 		urls.add(url);
 		return getThis();
@@ -163,6 +165,41 @@ abstract class SitemapGenerator<U extends ISitemapUrl, THIS extends SitemapGener
 		return outFiles;
 	}
 	
+	/**
+	 * Writes out the sitemaps as a list of strings.
+	 * Each string in the list is a formatted list of URLs.
+	 * We return a list because the URLs may not all fit --
+	 * google specifies a maximum of 50,000 URLs in one sitemap.
+	 * @return a list of XML-formatted strings
+	 */
+	public List<String> writeAsStrings() {
+		List<String> listOfSiteMapStrings = new ArrayList<String>();
+		for (int start = 0; start < urls.size(); start += maxUrls) {
+			int end = start + maxUrls;
+			if (end > urls.size()) {
+				end = urls.size();
+			}
+			StringBuilder sb = new StringBuilder();
+			writeSiteMapAsString(sb, urls.subList(start, end));
+			listOfSiteMapStrings.add(sb.toString());
+		}
+		return listOfSiteMapStrings;
+	}
+	
+	private void writeSiteMapAsString(StringBuilder sb, List<U> urls) {
+		sb.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n");
+		sb.append("<urlset xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\" ");
+		if (renderer.getXmlNamespaces() != null) {
+			sb.append(renderer.getXmlNamespaces());
+			sb.append(' ');
+		}
+		sb.append(">\n");
+		for (U url : urls) {
+			renderer.render(url, sb, dateFormat);
+		}
+		sb.append("</urlset>");
+	}
+	
 	/** After you've called {@link #write()}, call this to generate a sitemap index of all sitemaps you generated.  
 	 * 
 	 */
@@ -179,6 +216,9 @@ abstract class SitemapGenerator<U extends ISitemapUrl, THIS extends SitemapGener
 	}
 	
 	private void writeSiteMap() {
+		if (baseDir == null) {
+			throw new NullPointerException("To write to files, baseDir must not be null");
+		}
 		if (urls.size() == 0) return;
 		String fileNamePrefix;
 		if (mapCount > 0) {
@@ -208,18 +248,9 @@ abstract class SitemapGenerator<U extends ISitemapUrl, THIS extends SitemapGener
 	}
 	
 	private void writeSiteMap(OutputStreamWriter out) throws IOException {
-		out.write("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"); 
-		out.write("<urlset xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\" ");
-		
-		if (renderer.getXmlNamespaces() != null) {
-			out.write(renderer.getXmlNamespaces());
-			out.write(' ');
-		}
-		out.write(">\n");
-		for (U url : urls) {
-			renderer.render(url, out, dateFormat);
-		}
-		out.write("</urlset>");
+		StringBuilder sb = new StringBuilder();
+		writeSiteMapAsString(sb, urls);
+		out.write(sb.toString());
 		out.close();
 	}
 	
diff --git a/src/main/java/com/redfin/sitemapgenerator/SitemapGeneratorOptions.java b/src/main/java/com/redfin/sitemapgenerator/SitemapGeneratorOptions.java
index a8b3aba..34c7ded 100644
--- a/src/main/java/com/redfin/sitemapgenerator/SitemapGeneratorOptions.java
+++ b/src/main/java/com/redfin/sitemapgenerator/SitemapGeneratorOptions.java
@@ -14,5 +14,13 @@ class SitemapGeneratorOptions extends
 	public SitemapGeneratorOptions(String baseUrl, File baseDir) throws MalformedURLException {
 		this(new URL(baseUrl), baseDir);
 	}
+	
+	public SitemapGeneratorOptions(URL baseUrl) {
+		super(baseUrl);
+	}
+	
+	public SitemapGeneratorOptions(String baseUrl) throws MalformedURLException {
+		super(new URL(baseUrl));
+	}
 
 }
diff --git a/src/main/java/com/redfin/sitemapgenerator/WebSitemapGenerator.java b/src/main/java/com/redfin/sitemapgenerator/WebSitemapGenerator.java
index fc7400b..a0814b0 100644
--- a/src/main/java/com/redfin/sitemapgenerator/WebSitemapGenerator.java
+++ b/src/main/java/com/redfin/sitemapgenerator/WebSitemapGenerator.java
@@ -1,8 +1,6 @@
 package com.redfin.sitemapgenerator;
 
 import java.io.File;
-import java.io.IOException;
-import java.io.OutputStreamWriter;
 import java.net.MalformedURLException;
 import java.net.URL;
 
@@ -57,6 +55,25 @@ public class WebSitemapGenerator extends SitemapGenerator<WebSitemapUrl,WebSitem
 		this(new SitemapGeneratorOptions(baseUrl, baseDir));
 	}
 
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public WebSitemapGenerator(String baseUrl) throws MalformedURLException {
+		this(new SitemapGeneratorOptions(new URL(baseUrl)));
+	}
+	
+	/**Configures the generator with a base URL and a null directory. The object constructed
+	 * is not intended to be used to write to files. Rather, it is intended to be used to obtain
+	 * XML-formatted strings that represent sitemaps.
+	 * 
+	 * @param baseUrl All URLs in the generated sitemap(s) should appear under this base URL
+	 */
+	public WebSitemapGenerator(URL baseUrl) {
+		this(new SitemapGeneratorOptions(baseUrl));
+	}
 	
 	private static class Renderer extends AbstractSitemapUrlRenderer<WebSitemapUrl> implements ISitemapUrlRenderer<WebSitemapUrl> {
 
@@ -64,13 +81,13 @@ public class WebSitemapGenerator extends SitemapGenerator<WebSitemapUrl,WebSitem
 			return WebSitemapUrl.class;
 		}
 		
-		public void render(WebSitemapUrl url, OutputStreamWriter out, W3CDateFormat dateFormat) throws IOException {
-			super.render(url, out, dateFormat, null);
-		}
-
 		public String getXmlNamespaces() {
 			return null;
 		}
 
+		public void render(WebSitemapUrl url, StringBuilder sb, W3CDateFormat dateFormat) {
+			super.render(url, sb, dateFormat, null);
+		}
+
 	}
 }
diff --git a/src/test/java/com/redfin/sitemapgenerator/SitemapGeneratorTest.java b/src/test/java/com/redfin/sitemapgenerator/SitemapGeneratorTest.java
index 1388612..dcfaca8 100644
--- a/src/test/java/com/redfin/sitemapgenerator/SitemapGeneratorTest.java
+++ b/src/test/java/com/redfin/sitemapgenerator/SitemapGeneratorTest.java
@@ -291,6 +291,31 @@ public class SitemapGeneratorTest extends TestCase {
 		assertEquals("sitemap didn't match", SITEMAP1, actual);
 	}
 	
+	public void testBaseDirIsNullThrowsNullPointerException() throws Exception {
+		wsg = WebSitemapGenerator.builder("http://www.example.com", null).autoValidate(true).maxUrls(10).build();
+		wsg.addUrl("http://www.example.com/index.html");
+		Exception e = null;
+		try {
+			wsg.write();
+		} catch (Exception ex) {
+			e = ex;
+		}
+		assertTrue(e instanceof NullPointerException);
+		assertEquals("Correct exception was not thrown", e.getMessage(), "To write to files, baseDir must not be null");
+	}
+	
+	public void testWriteAsStringsMoreThanOneString() throws Exception {
+		wsg = WebSitemapGenerator.builder("http://www.example.com", null).autoValidate(true).maxUrls(10).build();
+		for (int i = 0; i < 9; i++) {
+			wsg.addUrl("http://www.example.com/"+i);
+		}
+		wsg.addUrl("http://www.example.com/9");
+		wsg.addUrl("http://www.example.com/just-one-more");
+		List<String> siteMapsAsStrings = wsg.writeAsStrings();
+		assertEquals("First string didn't match", SITEMAP1, siteMapsAsStrings.get(0));
+		assertEquals("Second string didn't match", SITEMAP_PLUS_ONE, siteMapsAsStrings.get(1));
+	}
+	
 	private String writeSingleSiteMap(WebSitemapGenerator wsg) {
 		List<File> files = wsg.write();
 		assertEquals("Too many files: " + files.toString(), 1, files.size());