It’s easier this way…

<VirtualHost *:80>

    ServerName example.com
    Redirect permanent / https://example.com/
    ServerAdmin webmaster@localhost
    DocumentRoot /var/www/html

</VirtualHost>

<VirtualHost *:80>
    ServerName www.example.com
    Redirect permanent / https://example.com/
</VirtualHost>

thanks rushpro…im going to try this…xx
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error…when i restart the apache2 i got failed & when i checked the error log (fatal error and some sort of error things i can’t relate)
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anyway i got it worked..it is so simple..it goes like this:

you make vhost settings:

<VirtualHost *:80>

ServerName example.com
Redirect permanent / https://example.com/
ServerAdmin webmaster@localhost
DocumentRoot /var/www/html

</VirtualHost>

and then, you go Let’s Encrypt https://www.digitalocean.com/community/tutorials/how-to-secure-apache-with-let-s-encrypt-on-ubuntu-14-04

after that, you recheck you’re mydomain.com.conf (where you put you’re vhost settings) in the lower part you will get settings like this before the end of </VirtualHost>:

RewriteEngine on
RewriteCond %{SERVERNAME} =www.mydomain.com [OR]
RewriteCond %{SERVERNAME} =mydomain.com
RewriteRule ^ https://%{SERVERNAME}%{REQUESTURI} [END,NE,R=permanent]

i change mydomain.com to www.mydomain.com…

RewriteEngine on
RewriteCond %{SERVERNAME} =www.mydomain.com [OR]
RewriteCond %{SERVERNAME} =www.mydomain.com
RewriteRule ^ https://%{SERVERNAME}%{REQUESTURI} [END,NE,R=permanent]

i checked chrome and firefox so far it works for me..anyway thanks for your comment it gives me an idea.