title: How to make a static Calendar thread safe
body: <p>I'd like to use a Calendar for some static methods and use a static field:</p>
  
  <pre><code>private static Calendar calendar = Calendar.getInstance();
  </code></pre>
  
  <p>Now I read java.util.Calendar isn't thread safe. How can I make this thread safe (it should be <strong>static</strong>)?</p>