How to change paging url (base) ?

Apache Server
Wordpress Version 2.5
Plugin: Permalink Validator Version 0.6

domainname.com/category-base/categoryname/page/2/
In the above url, I want to change ‘page’ word to ‘mykeyword’. I have not removed the category-base, instead changed to some keyword using the wordpress admin dashboard.

I am a beginner in WordPress and PHP. I tried something on my own! If this approach is wrong please guide me the right steps. I can revert back the following changes.

I have made the following changes to the code:

WordPress -> wp-inclueds -> rewrite.php
Line-574: $pageregex = 'page/?([0-9]{1,})/?$'; >> to >> $pageregex = 'java/?([0-9]{1,})/?$';

WordPress -> wp-inclueds -> link-template.php
Line-638: $request = preg_replace( '|page/\d+/?$|', '', $request); >> to >>$request = preg_replace( '|java/\d+/?$|', '', $request);
Line-648:
$request = ( ( !empty( $request ) ) ? trailingslashit( $request ) : $request ) . user_trailingslashit( 'page/' . $pagenum, 'paged' );
>> to >>

$request = ( ( !empty( $request ) ) ? trailingslashit( $request ) : $request ) . user_trailingslashit( 'java/' . $pagenum, 'paged' );
Plugin: Permalink Validator -> In page: permalink-validator.php

Line-103: $link .= 'page/' . $paged . '/'; >> TO >> $link .= 'java/' . $paged . '/';

Line-143: $link .= 'page/' . $paged . '/'; >> TO >> $link .= 'java/' . $paged . '/';