title: java data structure to hold many arrays of ints and their labels
body: <p>I have input like this: </p>
  
  <pre><code>0, 0, 0, 0, 1, 0, 2,     A
  0, 0, 3, 0, 1, 0, 2,     A
  0, 2, 0, 0, 1, 0, 2,     B
  0, 0, 0, 0, 1, 0, 2,     A
  </code></pre>
  
  <p>With the letter being the label, and then numbers being the inputs. </p>
  
  <p>I'd like to store this whole matrix in one data structure, such that the inputs that correspond to a particular label can be associated with it. </p>
  
  <p>How to do this? </p>
  
  <p>With a 2d array? </p>
  
  <p>With an array list?</p>
  
  <p>Hashmap?</p>