javastaticinitializationclassloaderfinal

Java : in what order are static final fields initialized?

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);
}

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?

Solution

  • 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:

    Next, 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.