Add getExtension method with String parameter.

src/fr/devinsy/util/FileTools.java

@@ -114,10 +114,35 @@ public class FileTools
 		}
 		else
 		{
-			int separatorIndex = file.getName().lastIndexOf('.');
+			result = getExtension(file.getName());
+		}
+
+		//
+		return result;
+	}
+
+	/**
+	 * Get the extension of a file.
+	 * 
+	 * @param file
+	 *            Source.
+	 * 
+	 * @return Extension value or null.
+	 */
+	public static String getExtension(final String fileName)
+	{
+		String result;
+
+		if (fileName == null)
+		{
+			result = null;
+		}
+		else
+		{
+			int separatorIndex = fileName.lastIndexOf('.');
 			if (separatorIndex > 0)
 			{
-				result = file.getName().substring(separatorIndex + 1).toLowerCase();
+				result = fileName.substring(separatorIndex + 1).toLowerCase();
 			}
 			else
 			{