Can Synchronizing on a Local Variable in Java Actually Acquire a Lock?

Welcome to the "Internet Full-Stack Architecture" WeChat public account. The previous poll discussed the meaning of the number in MySQL integer type definitions such as int(2), clarifying that the number does not limit the stored value length but only affects display in some consoles.

In the current poll, the focus shifts to Java concurrency. The synchronized keyword is commonly used to lock code blocks or methods, and a code snippet is provided where synchronization is applied to a locally created String object.

private int count = 0;
public void testSync() {
    String str = new String("test");
    synchronized (str) {
        for (int i = 0; i < 10; i++) {
            count++;
        }
    }
}

The question posed to readers is whether this code truly acquires a lock, considering that the lock object is a local variable that is not shared across threads.

Readers are invited to share their answers and insights.