title: Find the average of numbers using MapReduce
body: <p>I have been trying to write some code to find the average of numbers using MapReduce.</p>
  
  <p>I am trying to use global counters to reach my goal but I am not able to set the counter value in the <code>map</code> method of my Mapper and I am also not able to retrive the counter value in the <code>reduce</code> method of my Reducer.</p>
  
  <p>Do I have to use a global counter in <code>map</code> anyway (e.g. by using <code>incrCounter(key, amount)</code> of the provided <code>Reporter</code>)? Or would you suggest any different logic to get the average of some numbers?</p>