how to delete the content of text file without deleting itself

Question

I want to copy the content of file \'A\' to file \'B\'. after the copying is done I want to clear the content of file \'A\' and want to write on it from its beginning. I can

Answer 1

FileOutputStream fos = openFileOutput("/*file name like --> one.txt*/", MODE_PRIVATE);
FileWriter fw = new FileWriter(fos.getFD());
fw.write("");