Переименовать файл

File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath() ...);
                    File file2 = new File(Environment.getExternalStorageDirectory().getAbsolutePath() ...);
                    file.renameTo(file2);

// Copy the source file to target file.
// In case the dst file does not exist, it is created
void copy(File source, File target) throws IOException {
 
    InputStream in = new FileInputStream(source);
    OutputStream out = new FileOutputStream(target);
 
    // Copy the bits from instream to outstream
    byte[] buf = new byte[1024];
    int len;
 
    while ((len = in.read(buf)) > 0) {
        out.write(buf, 0, len);
    }
 
    in.close();
    out.close();
}

builder.setPositiveButton(getResources().getString(R.string.yes), new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/DCIM/InfoSystem/Files/PhotoInfo.txt");
                    File file2 = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/DCIM/InfoSystem/Files/PhotoInfo" + Long.toString(System.currentTimeMillis()) + ".txt");
                    file.renameTo(file2);
                    MediaScannerConnection.scanFile(context,
                            new String[]{Environment.getExternalStorageDirectory().getAbsolutePath() + "/DCIM/InfoSystem"}, null,
                            new MediaScannerConnection.OnScanCompletedListener() {
                                public void onScanCompleted(String path, Uri uri) {
                                    Log.i("ExternalStorage", "Scanned " + path + ":");
                                    Log.i("ExternalStorage", "-> uri=" + uri);
                                }
                            });
                }
            });