In Java static fields are initialized when a class is loaded by the class loader. A class is only loaded when used. If anything (IO,scheduler,etc) changes the order in which classes are used, then initializers are called in a different order and their side effects as well. This semantic is mandatory by language definition.

In a Java AOT compiler this means every access to a static field must be prefixed with a (synchronized) check if the class is already initialized and optimizing it away is rarely possible. A JIT compiler does not even care, because it knows the class is already loaded.

For contrast, in C++ static fields are all initialized before main is called.

Now with Oracle taking the steps to eventually make AOT compilation also a feature in the reference JDK, I suppose whatever issues might still exist they will be tackled.