If you are using the JSP Tag, you can cache the generated HTML file so that next invocations use it instead of parsing the source file again. To do this, use the cache property, which specifies in which directory should the cached results be stored:
<c2w:convert input="Foo.java" cache="/WEB-INF/cache" ... />
When the convert tag finds the cache property, it first looks for a file called "Foo.html" in the /WEB-INF/cache directory. If it is there, the timestamp of that file is compared with the timestamp of the source. If the source has not been changed since the HTML file was generated, the HTML file is sent and no source processing is done. Otherwise, the source is parsed and the result is stored in the HTML file.
Of course, caching is meaningful only if you don't change any output options,as the resulting HTML file is fixed and no new options (or different) can be applied to it.