title: Need explantation about basic java operator :
body: <pre><code>/**
   * Returns all Comments of the given review
   * @param reviewId
   * @return Returns all Comments as Collection or an empty Collection, if no Comments exist
   */
  protected ArrayList&lt;Comment&gt; getComments(String reviewId) {
      ArrayList&lt;Comment&gt; result = new ArrayList&lt;Comment&gt;();
  
      HashMap&lt;String, TreeMap&lt;Integer, Comment&gt;&gt; authorMap = commentDB.get(reviewId);
      if (authorMap != null) {
          for (TreeMap&lt;Integer, Comment&gt; x : authorMap.values()) {
              result.addAll(x.values());
          }
      }
      return result;
  </code></pre>
  
  <p>In the following code, I am not understanding what is the use of <code>:</code> in the line </p>
  
  <pre><code>  for (TreeMap&lt;Integer, Comment&gt; x : authorMap.values()) 
  </code></pre>
  
  <p>I know <code>:</code> is a conditional operator, but don't know what conditional operator it is and what is its use. I searched java operators in google but did not found this operator.</p>