How do synchronized static methods work in Java?

Locking Mechanism in Synchronized Static Methods

In Java, synchronized methods guarantee that only one thread can execute a given method at any time. The mechanism involves acquiring a monitor to synchronize access.

Synchronizing Static Methods

For static methods, which don't belong to any specific object instance, it's not immediately clear how synchronization is handled. According to the Java documentation, "it is not possible for two invocations of synchronized methods on the same object to interleave." So, what happens in the case of static methods?

Acquiring Class Object Monitor

The Java Language Specification (JLS) clarifies this behavior: "For a class (static) method, the monitor associated with the Class object for the method's class is used." This means that when a synchronized static method executes, it acquires the monitor associated with the class object representing the class in which the method is defined.

In simpler terms, the synchronized keyword in a static method essentially locks on the class itself. So, only one thread can be executing any synchronized static method on a given class at any time. This ensures that no two threads can interleave while performing class-level operations.

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