title: how to rename file from sdcard/newfolder in android
body: <p>I have a file in directory called sdcard/newfolder. I want to rename files from newfolder directory. I have following line of code its working for files from sdcard but not for newfolder.</p>
  
  <pre><code>File sdcard = Environment.getExternalStorageDirectory();
  File from = new File(sdcard,("a.txt"));
  File to = new File(sdcard,("b.txt"));
  from.renameTo(to); 
  </code></pre>
  
  <p>can anyone help me to solve this problem.
  thanks in advance</p>