java - 当多个线程同时请求加载同一个类时会发生什么？

Question

在多线程环境下，当多个线程同时引用一个类时，JVM 是否最终会多次加载该类？

如果不是，同步是如何发生的？

Answer 1

该类将被加载一次。参见 jls 12.4.2

For each class or interface C, there is a unique initialization lock LC. The mapping from C to LC is left to the discretion of the Java Virtual Machine implementation. The procedure for initializing C is then as follows:

1. Synchronize on the initialization lock, LC, for C. This involves waiting until the current thread can acquire LC.

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