What are the thread synchronization mechanisms in Java parallel programming?

Thread synchronization mechanisms in Java parallel programming include: Lock: forcing only one thread to execute at a time within a specific code block. Semaphore: Limits the number of threads that can access shared resources at the same time. Atomic variables: Guaranteed to read and update values ​​atomically within a thread. Synchronous container: A container class with built-in synchronization mechanism. Volatile variables: ensure that different threads can always see the latest value of the data.

Thread synchronization mechanism in Java parallel programming

The synchronization mechanism is a crucial part to ensure that concurrent code runs correctly and reliably . In Java parallel programming, there are various synchronization mechanisms available to prevent multiple threads from accessing shared resources simultaneously, leading to unexpected behavior and data corruption.

Synchronization mechanism type

• Lock: An explicit synchronization mechanism that forces only one block of code to be executed at a time. There can be one thread of execution.
• Semaphore: A mechanism that limits the number of threads that can access shared resources at the same time.
• Atomic variable: A special type of variable that guarantees that values ​​can be read and updated atomically within a thread.
• Synchronization container: A container class designed for concurrent use with built-in synchronization mechanism.
• volatile variable: A special type of variable that ensures that different threads can always see the latest value of the data, even in a multi-threaded environment.

Practical case

Consider a class containing a shared counterCounter:

public class Counter {
    private int count;

    public void increment() {
        count++;
    }
}

If the synchronization mechanism is not used , multiple threads may call the increment() method at the same time, resulting in unpredictable counting results. To solve this problem, you can add the synchronized keyword to the code block:

public class Counter {
    private int count;

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

This will create a lock to ensure that only one thread can execute increment() at a time method, thereby preventing data races.

Conclusion

Thread synchronization mechanism is crucial to ensure the correctness of Java parallel code. By understanding and correctly applying these mechanisms, developers can create controlled, efficient concurrent applications.

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