title: Why is an ArrayList of ArrayLists not multidimensional?
body: <p>I recently appeared for an interview in which the interviewer asked me a question regarding <code>Arrays</code> and <code>ArrayList</code>. </p>
  
  <p>He asked me if an array of arrays can be multidimensional, then why is an <code>ArrayList</code> of <code>ArrayList</code>'s not multidimensional? </p>
  
  <p>For example:</p>
  
  <pre><code>// Multidimensional
  int[][] array = new int[m][n]; 
  
  // Not multidimensional
  ArrayList&lt;ArrayList&lt;Integer&gt;&gt; seq = new ArrayList&lt;ArrayList&lt;Integer&gt;&gt;(); 
  </code></pre>
  
  <p>Can anyone help me to understand this?</p>