I'm not sure how this even relates to java, nor what the exact problem is. Creating an entry page should be as easy as creating an index.html page containing the appropriate content/links - yet if an index.html already exists you may need to be careful to make sure you want to overwrite the content of this file without breaking anything. If you wish to have this page display the first time a user visits, then you will need a more complex solution requiring sessions/cookies. Wordpress may have a plugin that accomplishes either of these, so search for one if you have not.
All this being said, an entry page such as this (if I understand you correctly) is frowned upon by many - it makes it difficult for users to get to the content they want to get to (and in many cases results in more exits than entries) as well as making it more difficult for a web crawler to understand the content of your website (and depending upon design could be considered a 'doorway' page, something frowned upon by search engines).