Use String replace function to make sure the output file extension is .xls

Using String replace function to make sure the output file extension is .xls. Below is example code:
int rVal = c.showSaveDialog(SaveButton.this);
  if (rVal == JFileChooser.APPROVE_OPTION) {
    String str = c.getSelectedFile().getName();
    _filename = str.replace(".xls", "");
    _dir = c.getCurrentDirectory().toString();
    _fullpath = _dir + "\\" + _filename + ".xls";
    _file = new File(_fullpath);