Java:静态最终字段的初始化顺序是什么?

Java : in what order are static final fields initialized?(Java:静态最终字段的初始化顺序是什么?)

问题描述

好的，假设我有一个看起来像这样的课程:

Okay, so say I have a class that looks like this :

public class SignupServlet extends HttpServlet {
    private static final Logger SERVLET_LOGGER=COMPANYLog.open(SignupServlet.class);
    private static final ExceptionMessageHandler handler = new ExceptionMessageHandler();   
    private static final SignupServletObservableAgent signupObservableAgent = 
        new SignupServletObservableAgent(null, SERVLET_LOGGER);
}

我可以指望类加载器按顺序初始化这些字段，以便我可以依赖 SERVLET_LOGGER 在 signupObservableAgent 之前实例化吗?

Can I count on the class loader to initialize those fields in order, such that I can rely on SERVLET_LOGGER to be instantiated before signupObservableAgent?

推荐答案

是的，它们按照它们在源代码中出现的顺序进行初始化.您可以在 Java 语言规范，§12.4.2.见第 9 步，内容如下:

Yes, they are initialized in the order in which they appear in the source. You can read all of the gory details in The Java Language Specification, §12.4.2. See step 9, which reads:

... 执行类的类变量初始化器和静态初始化器，或者接口的字段初始化器，按照文本顺序，就好像它们是一个单独的块一样，除了最终的类变量和接口的字段的值是编译时常量首先被初始化...

... execute either the class variable initializers and static initializers of the class, or the field initializers of the interface, in textual order, as though they were a single block, except that final class variables and fields of interfaces whose values are compile-time constants are initialized first ...

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