LANG-1435: Implemented defaultIfNull method that uses a supplier for default value

[dekelpilli]

From JIRA ticket:

Currently, if the default value in defaultIfNull is computationally slow (for example, it requires a database call, or complex calculations), it's not worth using the util method. This feature is to implement a method that would only perform this computationally slow action if the object value is actually null. This can be done using a Supplier.

In short, you'd call ObjectUtils.getDefaultIfNull(someNullableValue, DbUtil::doGet) instead of ObjectUtils.defaultIfNull(someNullableValue, DbUtil.doGet())

[MarkDacek]

I'm curious whether this is worthwhile given the existence of ObjectUtils.firstNonNull. Is the supplier that much of a necessity?

The only plus I see is that it wouldn't be executed if the default isn't null. Is that a major performance increase for a significant number of use-cases?

[PascalSchumacher]

Thanks for the pull request!

Java 11 offers Objects#requireNonNullElseGet (see https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Objects.html#requireNonNullElseGet(T,java.util.function.Supplier) for details), so I don't think we should add this.

[chtompki]

Ok we’ll close this I think. Many thanks all.

[dekelpilli]

I think it's useful, but I agree, if J11 has it then we shouldn't double up.

[mikkomaunu]

Method suggested here serves slightly different use case and cannot always be substituted by java.lang.Objects#requireNonNullElseGet. As 'requireNonNull' in name hints, requireNonNullElseGet will throw NullPointerException if Supplier that returns null is utilized.