title: Java initialize map with keys from set
body: <p>In java, can you initialize a new map's keyset based on the values of an existing set?</p>
  <p>Something like:</p>
  <pre><code>Set&lt;String&gt; setOfStrings = getSetFromSomeOtherFuntion();
  
  Map&lt;String, Boolean&gt; map = new Hashmap&lt;&gt;(setOfStrings);
  </code></pre>
  <p>If that's possible, then I would presume the value for each entry in the map is null, which is ok, but even better would be if a default value could be set (for example, false if it's Boolean).</p>