title: if (String != null && !String.isEmpty()) not working for checking null
body: <p>I am checking String whether it's null or not but I don't know why it's always enter into <code>if block</code> </p>
  
  <pre><code> Log.d(TAG,"String ID  "+str);
   if (str!= null &amp;&amp; !str.isEmpty()){
      Log.d(TAG,"String ID is not Null ");                 
   } else {
      Log.d(TAG,"String ID is Null ");            
   }
  </code></pre>
  
  <p>I also generate logs to check String value before checking if condition and it shows like this</p>
  
  <pre><code>01-06 07:17:46.128 30321-30376/com.example D/### String Checker ###: Page ID  null
  01-06 07:17:46.128 30321-30376/com.example D/### String Checker ###: Page ID is not Null 
  </code></pre>
  
  <p><strong>Update:</strong>
  Setting String to <code>null</code> then calling other class like this</p>
  
  <pre><code>String str = null;
  new AsyncTask(searchInterfaceChat,getActivity(),String.valueOf(str)).execute(query);
  </code></pre>