title: Java string null check by != null or !str.equals(null)?
body: <p>What's the best way to check for not null values in java.</p>
  
  <pre><code>String query ="abcd";
  </code></pre>
  
  <p><code>query != null</code> vs  <code>!query.equals(null).</code></p>
  
  <p>which is better?why?</p>