Hello everyone, I am Xiaomi! Today, we are going to talk about a very important topic in Java multithreaded programming: the difference between Synchronized and Volatile. These two keywords are often confusing, but they are indispensable tools for us to write efficient and stable multi-threaded programs. Not much nonsense, let us analyze it in depth!
Synchronized VS Volatile
First, let's start with a simple list to compare the main differences between Synchronized and Volatile:
In-depth analysis: Synchronized
Synchronized, called "synchronization lock" in Chinese, is one of the most basic synchronization mechanisms in Java. It achieves mutually exclusive access to the critical section (Critical Section) by acquiring the lock of the object . When a thread enters a Synchronized code block or method, it automatically acquires the lock, and other threads must wait for the thread to release the lock before entering. This ensures the atomicity and thread safety of the critical section code.
However, Synchronized also has some shortcomings. First , it creates a performance overhead because of the lock acquisition and release involved . Secondly, if there are many nested synchronization blocks, it is easy to cause deadlock . In addition, Synchronized can only act on code blocks and methods, which limits its application scenarios .
In-depth analysis: Volatile
Volatile, called "volatile variable" in Chinese, is another keyword used in multithreaded programming. It is mainly used to ensure the visibility of variable modifications to all threads, that is, once a thread modifies a Volatile variable, other threads will immediately see the change . This is useful in some simple scenarios, such as marking whether a thread should terminate.
However, Volatile does not guarantee atomicity . Although reading and writing Volatile variables themselves are atomic operations, compound operations (such as increment and decrement) may still not be atomic. In addition, Volatile can only be used to modify instance variables and class variables (static variables), and cannot be used for methods or code blocks .
How to choose: Synchronized or Volatile?
When we choose to use Synchronized or Volatile, we need to decide based on the specific situation. Here are some suggestions:
- If you need to ensure the atomicity and thread safety of critical section code and involve complex synchronization requirements, Synchronized may be more suitable.
- If you only need to ensure the visibility of variables, and read and write operations are relatively simple, then Volatile may be a better choice.
- If performance is an important consideration, consider using other more advanced synchronization mechanisms, such as ReentrantLock, instead of Synchronized.
END
Through today's sharing, we have an in-depth analysis of the differences between Synchronized and Volatile. Synchronized ensures the atomicity and thread safety of critical section code, but has a large performance overhead. Volatile guarantees the visibility of variables, but does not guarantee atomicity, and is suitable for simpler read and write operations. In actual programming, we need to choose an appropriate synchronization mechanism according to specific situations to achieve efficient and stable multi-threaded programs.
I hope that today’s sharing can help everyone better understand and apply Synchronized and Volatile, and add a powerful tool to multi-threaded programming! If you have more questions about this topic or want to discuss it in depth, please leave a message in the comment area and let’s discuss and communicate together. Thank you for reading, see you next time!
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