java - synchronized修饰代码块括号后面锁失效？

Answer 1

You can refer to my blog

The use of Synchronized for thread synchronization

Thread synchronization: Application of Synchronized in singleton mode

Answer 2

This blog has the answer. However, the reference to global lock is easily misleading. Because sychoronized 是使用括号里的对象来上锁，而 String.class is not all instances of the String class, but an object, an object of type Class. Therefore, if you use different such class objects to synchronize, you will obtain different locks.