Yes, static initializer blocks are guaranteed to execute in textual order. From the JLS, section 12.4.1: The intent is that a class or interface type has a set of initializers that put it in a consistent state, and that this state is the first state that is observed by other classes. The static initializers and … Read more
I wrote the spec. The TL; DR version of this answer is that just because it may see 0 for y, that doesn’t mean it is guaranteed to see 0 for y. In this case, the final field spec guarantees that you will see 3 for x, as you point out. Think of the writer … Read more
An official proposal has been made to allow static methods in interfaces in Java 7. This proposal is being made under Project Coin. My personal opinion is that it’s a great idea. There is no technical difficulty in implementation, and it’s a very logical, reasonable thing to do. There are several proposals in Project Coin … Read more
Note that the wording in the JLS of that particular section has changed significantly since then. It now (JLS 11) reads: 15.9.5. Anonymous Class Declarations: An anonymous class is never final (§8.1.1.2). The fact that an anonymous class is not final is relevant in casting, in particular the narrowing reference conversion allowed for the cast … Read more
Capture conversion was designed to make wildcards (in generics), ? useful. Suppose we have the following class: public interface Test<T> { public void shout(T whatever); public T repeatPreviousShout(); } and somewhere on our code we have, public static void instantTest(Test<?> test) { System.out.println(test.repeatPreviousShout()); } Because test is not a raw Test and since repeatPreviousShout() in … Read more
Because the integer overflows. When it overflows, the next value is Integer.MIN_VALUE. Relevant JLS If an integer addition overflows, then the result is the low-order bits of the mathematical sum as represented in some sufficiently large two’s-complement format. If overflow occurs, then the sign of the result is not the same as the sign of … Read more
I think you found this bug in the compiler: JDK-8029718 (or this similar one in Eclipse: 434642). Compare to JLS §15.12.2.1. Identify Potentially Applicable Methods: … A lambda expression (§15.27) is potentially compatible with a functional interface type (§9.8) if all of the following are true: The arity of the target type’s function type is … Read more
You can always cast to what you need, like this return (Class<List<String>>) new ArrayList<String>().getClass(); or return (Class<List<String>>) Collections.<String>emptyList().getClass(); But I assume that’s not what you are after. Well it works, with a warning, but it isn’t exactly “beautiful”. I just found this Why is there no class literal for wildcard parameterized types? Because a wildcard … Read more
Member variables cannot be overridden like methods. The number variables in your classes Beta and Gama are hiding (not overriding) the member variable number of the superclass. By casting you can access the hidden member in the superclass.