title: Fast conversion of single dimension array to two dimensional 'column' array
body: <p>Are there any built-in functions (or fast implementations) in Java to convert a single-dimension array of size <code>[n]</code> to a two-dimensional array of size <code>[n][1]</code>?</p>
  <p>For example:</p>
  <pre><code>double[] x = new double[]{1, 2, 3};
  double[][] x2D = new double[][]{{1}, {2}, {3}};
  </code></pre>