title: Java String hashCode of null string
body: <p>Only interesting, why method hashCode() in java.lang.String is not static?
  And in case of null return e.g. -1 ?
  Because frequently need do somethihg like:</p>
  
  <pre><code>String s;
  .............
  if (s==null) {
    return 0;}
  else {
    return s.hashCode();
  }
  </code></pre>
  
  <p>Thanks.</p>