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

[Peter Levart]

On 10/06/2015 04:11 PM, Paul Benedict wrote:
> If the second value is allowed to be null, then I don't find this new
> method useful. What value do you see in it? It doesn't provide any extra
> functionality to a simple if-else/ternary test, right? I throw my lot in
> with Stephen that the return value must be non-null.

The extra functionality of such function is that it can be used as an 
in-line expression. Ternary test requires to evaluate 1st argument twice 
or it can't be an expression:

T x = expression that is costly to compute;
(x == null) ? y : x

vs.

nullValue(expression that is costly to compute, y)


You can always compose:

nonNull(nullValue(x, y))


Regards, Peter

P.S. nullValue is my suggestion for the name (Oracle DB uses NVL(x, y))

P.P.S Current alternative is also: Optional.ofNullable(x).orElse(y)


>
>
> Cheers,
> Paul
>
> On Tue, Oct 6, 2015 at 9:06 AM, Roger Riggs <Roger.Riggs at oracle.com> wrote:
>
>> Hi Paul,
>>
>> Hence the question about the method name.
>> It already documents explicitly that the nullDefault value is returned and
>> does not restrict the value.
>>
>> To be a direct replacement for the current code, it should return the 2nd
>> value regardless of whether it is null or not.
>>
>> Roger
>>
>>
>>
>>
>> On 10/6/2015 9:56 AM, Paul Benedict wrote:
>>
>> It's quite possible for the second argument to be null. Is that your
>> intention? I am not sure it makes sense, but it's not harmful either. I
>> recommend you can either (1) explicitly document that's a possibility and
>> this method could still return null or (2) prevent it by calling
>> requireNonNull.
>>
>>
>> Cheers,
>> Paul
>>
>> On Tue, Oct 6, 2015 at 8:43 AM, Roger Riggs <Roger.Riggs at oracle.com>
>> wrote:
>>
>>> Java.lang.Objects contains a number of convenience methods to make it
>>> easier to handle references that are null.
>>> For example, toString(obj, nullDefault),
>>>
>>> A new method is proposed to return the reference or a default value if
>>> the reference is null.
>>>     static <T> T nonNull(T obj, T nullDefault);
>>>
>>> Alternatives to the method name include
>>> nonNullOrElse ( using the java.util.Optional name pattern) or
>>> nonNullOrDefault
>>>
>>> Please review and comment.
>>>
>>> Webrev:
>>>    http://cr.openjdk.java.net/~rriggs/webrev-object-non-null/
>>>
>>> Issue:
>>>    https://bugs.openjdk.java.net/browse/JDK-8138963
>>>
>>> Thanks, Roger
>>>
>>>
>>