title: Stream, return value of characters that didn't pass the filter
body: <p>I would like to count the characters that didn't pass the filter, and return this value too. How can i do that?</p>
  <p>My exc:
  Within class <code>LambdasStreamExercise</code>, implement method <code>dnaToWeight</code> in order to determine the molecular weight of a DNA sequence string from its nucleotides. Implement these individual steps in your stream:</p>
  <ul>
  <li>Start with <code>DNA.chars()</code> to initiate a Stream. This will be one of integers.</li>
  <li>Filter out those that do not represent regular DNA (Challenge: and count them)</li>
  <li>Convert to a stream of Character objects from the given DNA sequence</li>
  <li>Convert the Characters into Nucleotide objects</li>
  <li>Convert the Nucleotide objects to their weights</li>
  <li>Sum the weights and return the result (And report the number of rejected nucleotides)</li>
  </ul>
  <pre><code> public static double dnaToWeight(String DNA) {
          double dnaWeightTotal = DNA.chars()
                  .filter(c -&gt; c == 'A' || c == 'T' || c == 'G' || c == 'C')
                  .mapToObj(c -&gt; new Nucleotide((char) c))
                  .mapToDouble(c -&gt; (double) c.getWeight())
                  .sum();
          return dnaWeightTotal;
      }
  </code></pre>