ExecutorService停止并等待另一个ExecutorService在Java中完成

Question

I have two ExecutorService instances: One with 4 threads and the other, with 20 threads. I want that on a button click, Service 1 stops and waits for Service 2 to end. And afterwards, Service 1 continues to run.

I tried to do this with wait and notify but it's not working as expected:

ExecutorService 1:

    public void readFile(JTextArea textArea) {
    try {
        File file = new File(this.fm.fullPath);
        if (!file.exists()) {
            return;
        }
        BufferedReader br = new BufferedReader(new FileReader(this.fm.fullPath));

        ExecutorService executor = Executors.newFixedThreadPool(main.TOTALSTRINGS);

        String line = br.readLine();

        int i=1;
        while (line != null) {
            powThread t = new powThread("Thread" + (i+1), line, textArea);
            executor.execute(t);
            line = br.readLine();
            i++;
        }

        executor.shutdown();
        Thread t = new Thread() {
            public void run() {
                try {
                    executor.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
                    br.close();
                } catch (Exception e) {

                }
            }
        };
        t.start();

    } catch (IOException e) {
        e.printStackTrace();
    }
}

ExecutorService2 :

    public void generateNumStrings(JTextArea textArea) {
    StringGenerator sg = new StringGenerator();

    int[] dynamicThreads = main.calcThreadsTotal();
    int totalThreads = dynamicThreads.length;

    ExecutorService executor = Executors.newFixedThreadPool(totalThreads);

    for(int i=0; i<totalThreads; i++) {
        generateThread t = new generateThread("Thread" + (i+1), sg, dynamicThreads[i], this.fm);
        executor.execute(t);
    }

    executor.shutdown();

    Thread t = new Thread() {
        public void run() {
            try {
                textArea.setText("");
                executor.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
                textArea.append("File write successfully!");
            } catch (InterruptedException e) {

            }
        }
    };
    t.start();
}

Answer 1

You can use an AtomicReference in the first ExecutorService to wrap the second ExecutorService or null if the second ExecutorService hasn't been instantiated, then awaitTermination if the reference is non-null. I'm assuming that readFile and generateNumStrings are in the same class, if not then you'll need to find some way to make the AtomicReference visible to generateNumStrings

private final AtomicReference<ExecutorService> ref = new AtomicReference<>(null);

private void awaitTermination() throws InterruptedException {
    ExecutorService executor = ref.get();
    if(executor != null) {
        executor.awaitTermination(1, TimeUnit.DAYS);
    }
}

public void readFile(JTextArea textArea) {
...
    while (line != null) {
        awaitTermination();
        powThread t = new powThread("Thread" + (i+1), line, textArea);
        executor.execute(t);
        line = br.readLine();
        i++;
    }
...
}

public void generateNumStrings(JTextArea textArea) {
...
    ExecutorService executor = Executors.newFixedThreadPool(totalThreads);
    ref.set(executor);
...
}