如何使用四个线程打印1到10

Question

如何使用4线程打印1到10，当打印10号线程时，通知所有其他线程终止。我想要这样的输出

t1 -1
 t2 -2
 t3 -3
 t4 -4
 t1 -5
 t2 -6
 t3 -7
 t4 -8 
 t1-9       
 t2 -10
 all thread stop

我试过了，但我知道这不是正确的方法，有人能告诉我正确的方法吗?我在互联网上找不到正确的答案，如果有人告诉我正确的方法，那将是一个很大的帮助

public class NumberGame {
    public static void main(String[] args) {

        PrintSequenceRunnable.startFrom("T1");

        new Thread(new PrintSequenceRunnable("T1", "T2")).start();
        new Thread(new PrintSequenceRunnable("T2", "T3")).start();
        new Thread(new PrintSequenceRunnable("T3", "T1")).start();
    }
}

class PrintSequenceRunnable implements Runnable {

    private final String name;
    private final String next;

    private static String moveTo;

    private static int value = 1;

    PrintSequenceRunnable(String name, String next) {
        this.name = name;
        this.next = next;
    }

    static void startFrom(String start) {
        moveTo = start;
    }



    @Override
    public void run() {
        do {
            synchronized (moveTo) {
                if (name.equals(moveTo)) {
                    System.out.println(name + "-" + (value++));
                    moveTo = next;
                } else {
                    uselessCounter++;
                }
            }
        } while (value < 10);

    }

}

Answer 1

首先，如果你使用并发搜索线程安全的变量，对象和其他。永远不要使用像这样的private static int value = 1;，而要使用原子变量，例如private static AtomicInteger value = new AtomicInteger(0);。在你完成你的工作之前，你会一直做你的工作。如果任务已经完成，则中断线程。我有一段代码

类PrintSequenceRunnable实现了Runnable {

private final String name;
private final String next;

private static String moveTo;

private static AtomicInteger value = new AtomicInteger(0);

PrintSequenceRunnable(String name, String next) {
    this.name = name;
    this.next = next;
}

static void startFrom(String start) {
    moveTo = start;
}



@Override
public void run() {
    do {
            if (name.equals(moveTo) && value.get() < 10) {
                System.out.println(name + "-" + (value.incrementAndGet()));
                moveTo = next;
            }
    } while (value.get() < 10);
}

}

public static void main (String[] args) {
    PrintSequenceRunnable.startFrom("T1");

    new Thread(new PrintSequenceRunnable("T1", "T2")).start();
    new Thread(new PrintSequenceRunnable("T2" , "T3")).start();
    new Thread(new PrintSequenceRunnable("T3", "T4")).start();
    new Thread(new PrintSequenceRunnable("T4", "T1")).start();
}

输出：

T1-1
T2-2
T3-3
T4-4
T1-5
T2-6
T3-7
T4-8
T1-9
T2-10

Answer 2

要让线程在单个工作“队列”中工作，请使用LinkedBlockingQueue。在这里，我下载了几个线程，然后从视频中创建了一个90秒的预览，然后我将其上传到亚马逊S3。另外，我使用的是BlockingLinkedQueue，也许你应该使用PriorityQueue，它会自动在队列中为你的物品排序。

每个线程从队列中拉出一个项目，没有冲突、锁定等。

        BlockingQueue<String> filesToDownload = new LinkedBlockingDeque<String>(1024);
        BlockingQueue<String> filesToPreview = new LinkedBlockingDeque<String>(1024);
        BlockingQueue<String> filesToUpload = new LinkedBlockingDeque<String>(1024);

        String currentYear = String.valueOf(Calendar.getInstance().get(Calendar.YEAR));

        // DB connection.
        DB db = new DB();
        PreparedStatement st = null;
        Connection conn = null;
        conn = db.getConnection();

        // get ids from ats_store.products.
        try {

            st = conn.prepareStatement(sql);
            st.setString(1, currentYear);
            ResultSet rs = st.executeQuery();
            // add each id to IDS.
            while (rs.next()) {
                filesToDownload.add(rs.getString("product_id"));
                filesToPreview.add(rs.getString("product_id"));
                filesToUpload.add(rs.getString("product_id"));
            }
            conn.close();

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        int recordSize = filesToDownload.size();



        /**
         * Here we can find out how many cores we have.
         * Then make the number of threads NUMBER_OF_THREADS = the number of cores.
         */
        NUMBER_OF_THREADS = Runtime.getRuntime().availableProcessors();
        System.out.println("Thread Count: "+NUMBER_OF_THREADS);


        /**
         * 
         * CountDownLatch.we use this to block main until the working threads
         * are done working.
         */

        CountDownLatch startSignal = new CountDownLatch(1);
        CountDownLatch doneSignal = new CountDownLatch(NUMBER_OF_THREADS);

        // start up the Status Object class. For Reporting.
        Thread statusThread = new Thread(new Status(filesToDownload, currentYear, recordSize, "DOWNLOADING..."));
        statusThread.start();

        /**
         * prep downloader threads
         */
        Thread[] workers = new Thread[NUMBER_OF_THREADS];
        for (int x = 0; x < NUMBER_OF_THREADS; x++) {
            workers[x] = new Thread(new S3ObjectDownloader(filesToDownload, currentYear, startSignal, doneSignal));
            workers[x].start();
        }

        // start threads.
        startSignal.countDown();

        // block Main, wait for theads to complete.
        try {
            doneSignal.await();
        } catch (InterruptedException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }