know the features of your language

Then null will be returned, as the value of b.

Normally the purpose of a block of code like this is to provide a fallback hardcoded value if the dynamic value from your API or whatever is null. Like, setting a default title for a page of a notes app if the user didnt set a title themselves etc.

So, b is very likely to be a never-null, hardcoded value.

This code can still be valid and return null if b is null too, as the other person said.