title: Sorting a 2D arraylist based on first element of nested arraylist
body: <p>I'm having an issue whereby the original 2D arraylist, after sorting, outputs in the following format:</p>
  
  <pre><code>[639.5, 134, -2]
  [639.524, 131, -1]
  [640.478, 179, -2]
  [647.968, 192, -2]
  [649.068, 199, -2]
  [65.581, 3, -1]
  [66.387, 6, -1]
  [66.726, 7, -1]
  [660.182, 194, -1]
  </code></pre>
  
  <p>and I'd like to sort based on the first column only. Hence, my expected result should be this instead:</p>
  
  <pre><code>[65.581, 3, -1]
  [66.387, 6, -1]
  [66.726, 7, -1]
  [639.5, 134, -2]
  [639.524, 131, -1]
  [640.478, 179, -2]
  [647.968, 192, -2]
  [649.068, 199, -2]
  [660.182, 194, -1]
  </code></pre>
  
  <p>Somehow the <code>Collections.sort()</code> method sorts the list as if it's a String, hence "0" is bigger than ".", not knowing that the first column is made up of double values. Can anyone assist me in this? Thanks!</p>