Redirecting non www URL to www URL:

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

Redirecting the domain to a new subfolder of inside public_html:

RewriteEngine On
RewriteCond %{HTTP_HOST} ^xyz.com$ [OR]
RewriteCond %{HTTP_HOST} ^www.xyz.com$
RewriteCond %{REQUEST_URI} !^/new/
RewriteRule (.*) /new/$1



Result:
It will redirect from xyz.com/new to xyz.com