title: write a file to a folder in the android device internal storage
body: <p>I have a folder, called MyFolder, in the android device internal storage root directory. There is no external sd card mounted. The folder can be checked using says, ES file manager
   I want to write a file to that directory.
   I try the followings but seem all are not what I want. So how should sd be?
   Please help.</p>
  
  <pre><code>    File sd = Environment.getExternalStorageDirectory();
      //      File sd = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS)  ;
      //      File sd = new File( Environment.getExternalStorageDirectory().getAbsolutePath());
      //      File sd = Environment.getRootDirectory()  ; // system
      //      File sd = Environment.getDataDirectory()  ; 
  
  
      backupDBPath = "MyFolder/_subfolder/mydata.txt";
  
      File backupDB = new File(sd, backupDBPath);
  </code></pre>