In-depth exploration of concurrent programming of wait and notify methods in Java

Concurrent programming in Java has always been one of the important topics that developers need to understand and master in depth. In concurrent programming, controlling the collaboration and communication between threads is crucial, and the wait and notify methods are key tools. This article will delve into the principles, usage, and specific code examples of wait and notify methods in Java to help readers better understand these two important methods in concurrent programming.

The wait and notify methods are two important methods in the Object class. They are usually used to achieve collaboration and communication between threads. The wait method is used to put the current thread into a waiting state and release the object's lock, while the notify method is used to wake up a waiting thread. By combining the wait and notify methods, synchronization and collaboration between threads can be achieved to ensure orderly execution between threads.

First, let us take a look at the basic usage and principles of wait and notify methods. Before using the wait and notify methods, you need to obtain the object's lock first, which can be achieved through the synchronized keyword. Once the object's lock is acquired, the wait method can be called to put the thread into a waiting state and the object's lock is released; and the notify method can be called to wake up a waiting thread. It should be noted that the wait and notify methods must be called in synchronized code blocks or methods, otherwise an IllegalMonitorStateException will result.

Below, let us demonstrate the usage of wait and notify methods through a specific code example.

public class WaitNotifyExample {
    public static void main(String[] args) {
        final Object lock = new Object();

        // 等待线程
        Thread waitThread = new Thread(() -> {
            synchronized (lock) {
                System.out.println("等待线程开始等待...");
                try {
                    lock.wait(); // 线程进入等待状态，并释放锁
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("等待线程被唤醒");
            }
        });

        // 唤醒线程
        Thread notifyThread = new Thread(() -> {
            synchronized (lock) {
                System.out.println("唤醒线程开始唤醒等待线程...");
                lock.notify(); // 唤醒等待线程
            }
        });

        waitThread.start();
        notifyThread.start();
    }
}

In this example, we create a waiting thread and a wake-up thread, which share the same object lock. In the waiting thread, we first acquire the object lock, and then call the wait method to put the thread into the waiting state and release the lock. In the wake-up thread, we also first obtain the object lock, and then call the notify method to wake up the waiting thread. In this way, we achieve collaboration and communication between threads.

In addition to the basic wait and notify methods, Java also provides wait (long timeout) and notifyAll () methods. wait(long timeout) can specify the waiting time of the thread, which will automatically wake up after the specified time; notifyAll() can wake up all waiting threads. The flexible use of these methods can better meet different concurrent programming needs.

In short, the wait and notify methods are important tools for realizing inter-thread collaboration and communication in Java, and play an important role in concurrent programming. By in-depth understanding of the principles and usage of these two methods, combined with specific code examples, we can better master the thread management and collaboration skills in concurrent programming, and improve the performance and reliability of the program. I hope this article can help readers gain a deeper understanding of concurrent programming.

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