title: How to count the number of occurrences of each word?
body: <p>If I have an article in English, or a novel in English, and I want to count how many times each words appears, what is the fastest algorithm written in Java?</p>
  
  <p>Some people said you can use Map &lt; String, Integer>() to complete this, but I was wondering how do I know what is the key words? Every article has different words and how do you know the "key" words then add one on its count?</p>