RFR 9: 8138963 : java.lang.Objects new method to default to non-null

Roger Riggs Roger.Riggs at Oracle.com
Wed Oct 7 22:24:26 UTC 2015


The original intent was to simplify the filling in of default values 
(even if null).
I took Remi's point about  the canonical coalescing operator not always 
returning non-null
but the push seems to be in the direction of making sure the result is 
always non-null.
I'd rather add a few very useful methods and avoid those with 
diminishing returns.

I note that nulls are discovered eventually, but doing more aggressive 
checking is preferred.
I expect the compiler is able to squeeze out all the extra checks.

In the current context of Objects that the jdk, I read the naming 
pattern of firstNonNull to imply
access to some sequential data structure like an array or list; but it 
doesn't gel with me to apply it to the arg list
(unless it was varargs).  The pattern of naming us "of"  as being 
factory producing an object
from the arguments seems apropos and is concise.

Please consider and comment:

     <T> T nonNullOf(T obj, T defaultObj);
     <T> T nonNullOf(T, obj, Supplier<T> defaultSupplier);

Details are in the updated webrev:

Regards, Roger

On 10/6/2015 6:42 PM, Remi Forax wrote:
> Null coalescing is a popular operator in several languages [1] and the usual semantics is nullOrElse and not firstNonNull.
> In languages like Kotlin or Swift, because there is a distinction between Object and Object?, it's not a big deal, you can not de-reference null by error, anyway.
> Also note that nullOrElseGet, the one that takes a supplier also exists in Groovy and Kotlin under the name null safe navigation.
> So even if i prefer the semantics of firstNonNull, i think we should also include both nullOrElse and nullOrElseGet.
> regards,
> Rémi
> [1] https://en.wikipedia.org/wiki/Null_coalescing_operator
> -

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