title: Convert from List<List<Integer>> to List<int[]>
body: <p>i want to convert from <code>List&lt;List&lt;Integer&gt;&gt;</code> to <code>List&lt;int[]&gt;</code> but i don't know how to do it.</p>
  
  <p>I try to do it :</p>
  
  <pre><code>List&lt;Integer&gt; list = new ArrayList&lt;&gt;();
  List&lt;List&lt;Integer&gt;&gt; arr = matrix(list);
  int [] temp2 = arr;
  </code></pre>
  
  <p>But it was wrong</p>