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

[Ivan Gerasimov]

On 06.10.2015 16:58, Roger Riggs wrote:
> Hi Ivan,
>
> Easy enough, but I have not surveyed the codebase to see if it would 
> be used or is necessary.
> Most of the cases I've seen are simple if/then/else or ?: expressions.
>
I found a few possible candidates with grep:

share/classes/java/net/InetSocketAddress.java: addr == null ? 
InetAddress.anyLocalAddress() : addr,
==> Objects.nonNull(addr, InetAddress::anyLocalAddress)

share/classes/java/net/InetAddress.java: throw ex == null ? new 
UnknownHostException(host) : ex;
==> throw Objects.nonNull(ex, () -> new UnknownHostException(host))

share/classes/java/util/TreeMap.java:            value = (defaultVal != 
null ? defaultVal : (V) str.readObject());
==>                                              value = 
Objects.nonNull(defaultVal, () -> (V) str.readObject())

share/classes/java/time/format/DateTimeFormatter.java: ParsePosition pos 
= (position != null ? position : new ParsePosition(0));
==> ParsePosition pos = Objects.nonNull(position, () -> new ParsePosition(0)
etc.

I'm not sure, though, they should be really changed, as using this 
nonNull() method doesn't really make the code shorter.

My point is that if someone wants to use Objects.nonNull() in a case, 
where the second argument is calculated, it would be better to provide 
her with that additional variant with Supplier.

Sincerely yours,
Ivan

> Using the Supplier for does have some extra overhead not readily 
> observable in the code.
> There is precedent for such a method in requireNonNull, where the cost 
> of composing/formatting
> the exception text can be avoided using a supplier.
>
> Roger
>
>
> On 10/6/2015 9:53 AM, Ivan Gerasimov wrote:
>> Hi Roger!
>>
>> I didn't notice the message, so first commented in the Jira.
>>
>> Would it make sense to also add a variant with the second argument of 
>> type Supplier, so that it can be lazily calculated only if needed?
>> Something like:
>> public static <T> T nonNull(T obj, Supplier<T> nullDefaultSupplier) {
>>     return (obj != null) ? obj : nullDefaultSupplier.get();
>> }
>>
>> Sincerely yours,
>> Ivan
>>
>> On 06.10.2015 16:43, Roger Riggs 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
>>>
>>>
>>
>