Non WWW to WWW redirection using htaccess File

Non WWW to WWW redirection  

This code using Htaccess, and also redirect index.html file to same directory in website. 

RewriteEngine on

RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /.*index\.html?\ HTTP/
RewriteRule ^(.*)index\.html?$ http://www.websitename.com/$1 [R=301,L]

RewriteCond %{HTTP_HOST} ^websitename\.com$
RewriteRule (.*) http://www.websitename.com/$1 [R=301,L]

For Examples

1. http://websitename.com

using above code
http://www.websitename.com

2.  http://websitename.com/index.html or http://www.websitename.com/index.html


using above code
http://www.websitename.com/