title: How to get the frequency of numbers in a list
body: <p>I have a list of five numbers (a hand of cards). I'd like to get the frequency of each number in the list, and put that in a map, or something similar.</p>
  
  <p>I know it's easy to implement this yourself. But I was curious, is there a way to do so in the Collections framework? </p>
  
  <hr>
  
  <p>(To be clear, not the frequency of any particular number, but the frequency of every number, in the list.)</p>