Pastable version of get path of a File relative to a directory

<pre class='prettyprint' language='java'>public static String getRelativePath(File file, File relativeTo) throws IOException {
		/*
		 * windows seems in some cases not to stop getParent() at 'c:\', which I
		 * considered to be root. For that reason I had to tweak in the
		 * following to 'ugly' lines:
		 */
		file = new File(file + File.separator + &quot;89243jmsjigs45u9w43545lkhj7&quot;).getParentFile();
		relativeTo = new File(relativeTo + File.separator + &quot;984mvcxbsfgqoykj30487df556&quot;).getParentFile();

File origFile = file;
		File origRelativeTo = relativeTo;
		ArrayList&lt;File&gt; filePathStack = new ArrayList&lt;File&gt;();
		ArrayList&lt;File&gt; relativeToPathStack = new ArrayList&lt;File&gt;();
		// build the path stack info to compare it afterwards
		file = file.getCanonicalFile();
		while (file != null) {
			filePathStack.add(0, file);
			file = file.getParentFile();
		}
		relativeTo = relativeTo.getCanonicalFile();
		while (relativeTo != null) {
			relativeToPathStack.add(0, relativeTo);
			relativeTo = relativeTo.getParentFile();
		}
		// compare as long it goes
		int count = 0;
		file = filePathStack.get(count);
		relativeTo = relativeToPathStack.get(count);
		while ((count &lt; filePathStack.size() - 1) &amp;&amp; (count &lt; relativeToPathStack.size() - 1) &amp;&amp; file.equals(relativeTo)) {
			count++;
			file = filePathStack.get(count);
			relativeTo = relativeToPathStack.get(count);
		}
		if (file.equals(relativeTo))
			count++;
		// up as far as necessary
		StringBuffer relString = new StringBuffer();
		for (int i = count; i &lt; relativeToPathStack.size(); i++) {
			relString.append(&quot;..&quot; + File.separator);
		}
		// now back down to the file
		for (int i = count; i &lt; filePathStack.size() - 1; i++) {
			relString.append(filePathStack.get(i).getName() + File.separator);
		}
		relString.append(filePathStack.get(filePathStack.size() - 1).getName());
		// just to test
		File relFile = new File(origRelativeTo.getAbsolutePath() + File.separator + relString.toString());
		if (!relFile.getCanonicalFile().equals(origFile.getCanonicalFile())) {
			throw new IOException(&quot;Failed to find relative path.&quot;);
		}
		return relString.toString();
	}</pre>
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Pastable version of get path of a File relative to a directory