What have you tried? So far we don' know if you're stuck reading a file, finding the string "java", counting or showing the results.
Some places to look in the JavaDoc: File & FileReader, String.indexOf(), Pattern & Matcher. See if any of those get you going. If you get part way and get stuck, show us some code and we'll help keep you moving.
Take small steps - don't try to write the whole program in one sitting - and have fun!
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi