Running a browser game in Java

I would like to know how I would kind of like run a online browser game, like tetris, as a Java application so I could control it (like in tetris using the wasd or arrow keys to move blocks) from within the application I program for the game. Not sure if that makes sense but don't know how else to explain it. The purpose is to hook it up to an AI program that plays the game, but yeah I don't know how to allow the program to control the game using the games allowed inputs.