+1 Paul.
> On 14 Feb 2017, at 10:52, Volker Simonis <volker.simo...@gmail.com> wrote: > > Hi, > > can I please have another review for the following trivial fix: > > http://cr.openjdk.java.net/~simonis/webrevs/2017/8174950/ > https://bugs.openjdk.java.net/browse/JDK-8174950 > > This change has already been discussed in length on the mailing list: > > http://mail.openjdk.java.net/pipermail/core-libs-dev/2017-February/thread.html#46324 > http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-February/thread.html#24989 > > and in the bug comments at: > > https://bugs.openjdk.java.net/browse/JDK-8033909 > > So I'll give just (yet another) short summary here: > > - Objects.requireNonNull(T, Supplier) does not check for the Supplier > argument being null. Instead it relies on the fact, that the VM will > implicitly throw a NullPointerException when it calls .get on the > Supplier argument during the creation of the explicit > NullPointerException which it is supposed to throw. > > - this behavior slightly differs from Objects.requireNonNull(T, > String) which simply creates a NullPointerException with a null > message in the case where the String argument is null. > > - the difference is not evident in the OpenJDK, because the HotSpot VM > creates a NPE with a null message by default if we call a method on a > null object. > > - however creating such a NPE with a null message when invoking a > method on a null object is not enforced by the standard, and other > implementations can do better :) For the following trivial program: > > public class NonNull { > public static void main(String[] args) { > Supplier<String> ss = null; > Object o = Objects.requireNonNull(null, ss); > } > } > > the current OpenJDK implementation returns: > > Exception in thread "main" java.lang.NullPointerException > at java.util.Objects.requireNonNull(Objects.java:290) > at NonNull.main(NonNull.java:8) > > but the SAP JVM will print: > > Exception in thread "main" java.lang.NullPointerException: while > trying to invoke the method java.util.function.Supplier.get() of a > null object loaded from local variable 'messageSupplier' > at java.util.Objects.requireNonNull(Objects.java:290) > at NonNull.main(NonNull.java:8) > > which is at least confusing for a call to Objects.requireNonNul() with > a null Supplier. We think the exception should be the same like the > one we get when invoking Objects.requireNonNul() with a null String. > > - because of this difference (and because we like our extended > Exception messages :) the JCK test for Objects.requireNonNul(T, > Supplier) (i.e. > api/java_util/Objects/index.html#RequireNonNullMessageSupplier) was > removed from TCK 8 and is still commented out in TCK 9 > (npe_checkingNullSupplier() in RequireNonNullMessageSupplier.java). > > I really think that the simplest and most natural fix for this problem > is to simply check for a null Supplier argument and create the NPE > with an explicit null message in that case (as outlined in the > webrev). This: > - makes the two requireNonNul() overloads for String and Supplier > behave the same (which I think was the initial intention). > - doesn't require documentation changes > - makes it possible to write a simple and conforming TCK test > > Regards, > Volker
