title: Scala SortedMap under the hood
body: <p>I use <code>SortedMap</code> for storing ordered elements:</p>
  
  <pre><code>val map = SortedMap("Kim" -&gt; 90, "Steve" -&gt; 22, "Alex" -&gt; 12)
  </code></pre>
  
  <p>My questions are:</p>
  
  <ol>
  <li>What is the implementation stand under <code>SortedMap</code>?</li>
  <li>Does <code>SortedMap</code> same to <code>Red black tree</code>?</li>
  <li><code>SortedMap</code> in Java is an interface, why in Scala it can be instantiated?</li>
  </ol>