try
      {
          new RandomAccessFile(file,"rw").setLength(0);
      }
      catch (FileNotFoundException e1)
      {
          // TODO Auto-generated catch block
          Log.i("Exception caught ==> ", e1.toString());
          e1.printStackTrace();
      }
      catch (IOException e)
      {
          // TODO Auto-generated catch block
          Log.i("Exception caught ==> ", e.toString());
          e.printStackTrace();
      }

RandomAccessFile ram = null;
    byte[] mydata = null;
    try
    {
        System.out.println("...rrunning my app...");
        String str =Environment.getExternalStorageDirectory().getAbsolutePath()+"/myfile.txt";
//      File f = new File(str);
        ram =new RandomAccessFile(str,"rw");
        ram.setLength(0);
        ram.write("i am fine".getBytes());
        System.out.println("...file length..."+ram.length());
        mydata = new byte[(int) ram.length()];
        ram.close();
        RandomAccessFile ram1 =new RandomAccessFile(str,"rw");
        ram1.read(mydata);
        System.out.println("...data present in 11file..."+new String(mydata));

    }
    catch (Exception e1)
    {
        // TODO Auto-generated catch block
        Log.i("Exception caught ==> ", e1.toString());
        e1.printStackTrace();
    }

try (FileOutputStream fos = new FileOutputStream("xxx")) {
    fos.write(new byte[0]);
}

try (FileWriter fw = new FileWriter("xxx")) {
    fw.write("");
}