如何使用 Java Shutdown Hooks 确保应用程序正常关闭并处理文件中的批处理？

<code class="java">public class GracefulShutdownTest2 {
    final private int N;
    final private File f;
    private volatile boolean keepRunning = true;

    public GracefulShutdownTest2(File f, int N) {
        this.f = f;
        this.N = N;
        registerShutdownHook();
    }

    public void run() {
        PrintWriter pw = null;
        try {
            FileOutputStream fos = new FileOutputStream(this.f);
            pw = new PrintWriter(fos);
            for (int i = 0; i < N && keepRunning; ++i) {
                writeBatch(pw, i);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            pw.close();
        }
    }

    private void writeBatch(PrintWriter pw, int i) {
        for (int j = 0; j < 100; ++j) {
            int k = i * 100 + j;
            pw.write(Integer.toString(k));
            if ((j + 1) % 10 == 0) {
                pw.write('\n');
            } else {
                pw.write(' ');
            }
        }
    }

    private void registerShutdownHook() {
        Runtime.getRuntime().addShutdownHook(new Thread() {
            @Override
            public void run() {
                keepRunning = false;
                try {
                    Thread.currentThread().join();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public static void main(String[] args) {
        if (args.length < 2) {
            System.out.println("args = [file] [N] "
                    + "where file = output filename, N=batch count");
        } else {
            new GracefulShutdownTest2(
                    new File(args[0]),
                    Integer.parseInt(args[1])
            ).run();
        }
    }
}</code>