Java thread synchronization and mutual exclusion: starting from scratch, creating efficient concurrent programs

Java thread synchronization and mutual exclusion are the keys to writing efficient concurrent programs. PHP editor Banana will take you from scratch to explore the thread synchronization mechanism in Java, allowing you to easily create efficient and stable concurrent programs and improve code quality and performance.

JavaThreadsOverview of Synchronization and Mutual Exclusion

In Java, thread synchronization and mutual exclusion are techniques to ensure that data races or other inconsistencies do not occur when multiple threads share data. Thread synchronization means that when multiple threads access shared data, they coordinate their access through some mechanism to ensure the consistency and integrity of the data. Thread mutual exclusion means that only one thread can access shared data, and other threads can only wait.

Java thread synchronization mechanism

Java provides a variety of thread synchronization mechanisms, the most common of which are locks and monitors. Locks are a low-level synchronization mechanism that allows a thread to acquire a lock before entering a critical section (that is, the block of code where shared data is located) and release the lock after exiting the critical section. The monitor is an advanced synchronization mechanism that combines locks and condition variables so that threads can sleep while waiting for the lock until the lock is released.

Java thread synchronization example

To better understand Java thread synchronization and mutual exclusion, let's look at a simple code example. In this example, we have two threads accessing a shared variable simultaneously. If there is no thread synchronization, it is very likely that two threads will modify the shared variables at the same time, resulting in data inconsistency.

public class SimpleSyncDemo {
private int sharedVariable = 0;

public void incrementSharedVariable() {
sharedVariable++;
}

public static void main(String[] args) {
SimpleSyncDemo demo = new SimpleSyncDemo();

Thread thread1 = new Thread(() -> {
for (int i = 0; i < 100000; i++) {
demo.incrementSharedVariable();
}
});

Thread thread2 = new Thread(() -> {
for (int i = 0; i < 100000; i++) {
demo.incrementSharedVariable();
}
});

thread1.start();
thread2.start();

try {
thread1.join();
thread2.join();
} catch (InterruptedException e) {
e.printStackTrace();
}

System.out.println("Shared variable value: " + demo.sharedVariable);
}
}

In this example, we use locks to synchronize shared variables. We first create a lock object, then in each thread, we acquire the lock before entering the critical section and release the lock after exiting the critical section. This way, we ensure that only a single thread can access the shared variable, thus avoiding data race issues.

Java thread mutual exclusion mechanism

Java thread mutual exclusion means that only one thread can access shared data, and other threads can only wait. The simplest way to achieve thread mutual exclusion is to use a mutex lock (Mutex). A mutex is a special type of lock that only allows one thread to acquire the lock, and other threads can only wait for the lock to be released.

Java thread mutual exclusion example

To better understand Java thread mutual exclusion, let's look at a simple code example. In this example, we have two threads accessing a shared variable simultaneously. If there is no thread mutual exclusion, it is very likely that two threads will modify the shared variables at the same time, resulting in data inconsistency.

public class SimpleMutexDemo {
private final Object lock = new Object();
private int sharedVariable = 0;

public void incrementSharedVariable() {
synchronized (lock) {
sharedVariable++;
}
}

public static void main(String[] args) {
SimpleMutexDemo demo = new SimpleMutexDemo();

Thread thread1 = new Thread(() -> {
for (int i = 0; i < 100000; i++) {
demo.incrementSharedVariable();
}
});

Thread thread2 = new Thread(() -> {
for (int i = 0; i < 100000; i++) {
demo.incrementSharedVariable();
}
});

thread1.start();
thread2.start();

try {
thread1.join();
thread2.join();
} catch (InterruptedException e) {
e.printStackTrace();
}

System.out.println("Shared variable value: " + demo.sharedVariable);
}
}

In this example, we use a mutex lock to achieve thread mutual exclusion. We first create a mutex object, then in each thread we acquire the mutex before entering the critical section and release the mutex after exiting the critical section. In this way, we ensure that only one thread can access the shared variable, thus avoiding data race problems.

Conclusion

Thread synchronization and mutual exclusion are essential basic knowledge in JavaConcurrent programming. Mastering these technologies can help us write efficient and reliable concurrency programs. In this article, we introduced the basics of Java thread synchronization and mutual exclusion, and demonstrated through code examples how to use these techniques to write concurrent programs.

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