是的，Java 静态初始值设定项是线程安全的(使用您的第一个选项).

Yes, Java static initializers are thread safe (use your first option).

但是，如果您想确保代码恰好执行一次，则需要确保该类仅由单个类加载器加载.每个类加载器执行一次静态初始化.

However, if you want to ensure that the code is executed exactly once you need to make sure that the class is only loaded by a single class-loader. Static initialization is performed once per class-loader.