@Override
public void onEvent(int event, String path) {
    if (event==DELETE) {
        File file = new File(rootPath, path);
        File otherFile = new File(rootPath, "backup_" + path);
        writeFile(file,otherFile);
    }
}

 private void writeFile(File inFile, File outFile) {
    Executors.newSingleThreadExecutor()
            .submit(() -> {
                 InputStream in;
                 OutputStream out;
                 try {
                     outFile.createNewFile();
                    in=new BufferedInputStream(new FileInputStream(inFile));
                    out=new BufferedOutputStream(new FileOutputStream(outFile));
                    byte[] data = new byte[2048];
                    while (in.read(data) > -1) {
                        out.write(data);
                    }
                    in.close();
                    out.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
}