Java thread synchronization and mutual exclusion: the cornerstone of multi-threaded programming, must know

Java thread synchronization and mutual exclusion are the cornerstones of multi-threaded programming and are crucial for Java programmers. PHP editor Yuzai will take you to understand this important concept in depth, discuss its principles, usage and common problems, allowing you to easily grasp the essence of multi-threaded programming.

Shared resources refer to resources that multiple threads can access at the same time, such as global variables or files, etc. When multiple threads access shared resources at the same time, data inconsistency may occur, causing program errors.

In order to avoid multi-thread conflicts, a synchronization mechanism needs to be used to ensure the atomicity of shared resources, that is, only one thread is allowed to access shared resources at a time. In Java, synchronization can be achieved using the synchronized keyword or the Lock interface.

The use of the synchronized keyword is very simple, just add the synchronized keyword before the method or code block. For example:

public class Counter {
private int value = 0;

public synchronized void increment() {
value++;
}
}

In this code, the increment() method is modified with the synchronized keyword, which means that only one thread can execute this method at a time. Therefore, even if multiple threads call the increment() method at the same time, there will be no data inconsistency.

The Lock interface provides more fine-grained synchronization control, which allows programmers to explicitly acquire and release locks . For example:

public class Counter {
private int value = 0;
private Lock lock = new ReentrantLock();

public void increment() {
lock.lock();
try {
value++;
} finally {
lock.unlock();
}
}
}

In this code, the lock.lock() method acquires the lock, and the lock.unlock() method releases the lock. Only the thread that acquires the lock can execute the increment() method, so multi-thread conflicts can also be avoided.

In addition to using the synchronization mechanism, you can also use mutex locks to achieve multi-thread synchronization. A mutex lock is a special lock that can only be held by one thread. Other threads must wait for the thread to release the lock before they can acquire the lock.

In Java, you can use the Mutex class or the synchronized keyword to implement a mutex lock. For example:

public class Counter {
private int value = 0;
private Mutex mutex = new Mutex();

public void increment() {
mutex.acquire();
try {
value++;
} finally {
mutex.release();
}
}
}

In this code, the mutex.acquire() method acquires the lock, and the mutex.release() method releases the lock. Only the thread that acquires the lock can execute the increment() method, so multi-thread conflicts can also be avoided.

In short, Java thread synchronization and mutual exclusion are important concepts in multi-threaded programming. Using the correct method can avoid multi-thread conflicts caused by shared resources.

The above is the detailed content of Java thread synchronization and mutual exclusion: the cornerstone of multi-threaded programming, must know. For more information, please follow other related articles on the PHP Chinese website!