How to solve thread priority issues in Java

How to solve the thread priority problem in Java

In Java multi-threaded programming, we can adjust the execution order of threads by setting the priority of the thread. Thread priority is an integer ranging from 1 to 10, where 1 is the lowest priority and 10 is the highest priority. The priority of a thread can be used to express the relative importance of a thread relative to other threads when competing for CPU resources.

However, in actual applications, we rarely rely directly on thread priorities to control the execution order of threads, because thread priorities may behave differently in different operating systems and JVM implementations. In order to avoid the uncertainty caused by thread priority issues, we should use other methods to control the execution order of threads.

The following are some commonly used methods to solve thread priority issues in Java:

1. Use the Thread.sleep() method: By making high-priority threads sleep for a period of time, let Low priority threads have a chance to execute. For example, we can add a Thread.sleep() statement to the task of a high-priority thread.

Thread highPriorityThread = new Thread(() -> {
    // 高优先级线程的任务
    Thread.sleep(1000);
});

Thread lowPriorityThread = new Thread(() -> {
    // 低优先级线程的任务
});

highPriorityThread.setPriority(Thread.MAX_PRIORITY);
lowPriorityThread.setPriority(Thread.MIN_PRIORITY);

highPriorityThread.start();
lowPriorityThread.start();

2. Use the wait() and notify() methods of the Object class: By using the wait() and notify() methods of the object, we can control the execution order of the threads. A high-priority thread can enter a waiting state while a low-priority thread is running, and then wake up the high-priority thread after the low-priority thread completes. For example:

Object lock = new Object();

Thread highPriorityThread = new Thread(() -> {
    synchronized (lock) {
        // 高优先级线程的任务
        try {
            lock.wait();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
});

Thread lowPriorityThread = new Thread(() -> {
    synchronized (lock) {
        // 低优先级线程的任务
        lock.notify();
    }
});

highPriorityThread.setPriority(Thread.MAX_PRIORITY);
lowPriorityThread.setPriority(Thread.MIN_PRIORITY);

highPriorityThread.start();
lowPriorityThread.start();

3. Use the thread's join() method: By using the thread's join() method, we can wait for other threads to complete their execution before continuing. The high-priority thread can wait when the low-priority thread calls the join() method until the low-priority thread completes execution before continuing. For example:

Thread highPriorityThread = new Thread(() -> {
    // 高优先级线程的任务
});

Thread lowPriorityThread = new Thread(() -> {
    // 低优先级线程的任务
});

highPriorityThread.setPriority(Thread.MAX_PRIORITY);
lowPriorityThread.setPriority(Thread.MIN_PRIORITY);

lowPriorityThread.start();
lowPriorityThread.join();
highPriorityThread.start();

In summary, although we can use thread priority to control the execution order of threads, in practical applications, we should avoid relying directly on thread priority. By using other methods such as Thread.sleep(), the wait() and notify() methods of the Object class, and the thread's join() method, we can better control the execution order of threads and avoid inconsistencies caused by thread priority issues. Certainty.

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