Change CSS class with Java

Is there a way to change the id for a CSS link with Java, so that it can remain active when clicked!?

This is my example of the css:

#inactive{
font-size:1.5em;
}

#active{
font-size:1em;
}

And the link:

<a href="" id="inactive">Link</a>

The idea is to make the link change into the #active id when clicked!