---

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Calendar;
import java.util.concurrent.locks.ReentrantLock;

public class FileHelper {

    public static final String FILE_NAME = "currentdata.txt";

    /** Общий замок для обоих потоков. */
    public static final ReentrantLock LOCK = new ReentrantLock();

    public static String currentTime() {
        Calendar c = Calendar.getInstance();
        return String.format("%1$tY-%1$tm-%1$td %1$tH:%1$tM:%1$tS", c);
    }

    public static String uniqueName() {
        Calendar c = Calendar.getInstance();
        return String.format("saved_%1$tY%1$tm%1$td_%1$tH%1$tM%1$tS_%1$tL.txt", c);
    }

    public static long fileSize() {
        File f = new File(FILE_NAME);
        return f.exists() ? f.length() : 0L;
    }

    public static void saveAndClear() throws IOException {
        File src = new File(FILE_NAME);
        if (!src.exists() || src.length() == 0) return;

        File dst = new File(uniqueName());
        if (!src.renameTo(dst)) {
            throw new IOException("Не удалось переименовать " + src.getName());
        }
        try (FileOutputStream fos = new FileOutputStream(FILE_NAME, false)) {
            // обнуление
        }
    }
}