Return Optional.absent() if value is null in Enums.getIfPresent

[GoogleCodeExporter]

Currently Enums.getIfPresent(enumClass, value) throws a NullPointerException if 
value is null.  It makes sense that it should throw this exception if enumClass 
is now, but it seems better to return Optional.absent() if value is null.  This 
way we can do something like Enums.getIfPresent(enumClass, 
value).or(someDefaultEnum) and if value is null, we get someDefaultEnum.  
Otherwise we need to wrap the call in either a catch for the 
NullPointerException, or check if value is null before checking if its a valid 
value of the enumClass.

Original issue reported on code.google.com by craig.skinfill on 23 Jan 2014 at 4:05

[GoogleCodeExporter]

Can you describe the code path that would lead to nulls being passed to 
Enums.getIfPresent in the first place?  Most of Guava's utilities are fairly 
strict about nulls in this same way, and this is commonly regarded as a good 
thing.

Original comment by wasserman.louis on 23 Jan 2014 at 4:08

[GoogleCodeExporter]

The actual code I'm working on is retrieving a string from an XML document.  I 
have some code in place now that converts that string into an enum, or returns 
a default but thought I'd use the Enums.getIfPresent instead.  Its possible 
(not likely, but possible) for this string to be null.  I changed the code to 
use Enums.getIfPresent and tripped a NPE when I ran some tests.  I've since 
reverted back to the original code.  With the null check in the getIfPresent 
method, its not as useful.  Given that null isn't a valid enum value, it seems 
that it should just return Optional.absent() if value is ever null.

Original comment by craig.skinfill on 23 Jan 2014 at 4:19

[GoogleCodeExporter]

As Louis mentioned, nearly all APIs in Guava will throw a NPE on null input. If 
you know you're dealing with null, how about:

import static com.google.common.base.Strings.nullToEmpty;

Enums.getIfPresent(enumClass, nullToEmpty(value))

Original comment by kak@google.com on 23 Jan 2014 at 5:05

• Changed state: WorkingAsIntended
• Added labels: Package-Base, Type-Enhancement

[GoogleCodeExporter]

Yes the nullToEmpty would work (i had forgotten about that one).  But I still 
feel that passing null for the value should just result in returning 
Optional.absent(), it doesn't seem to hurt anything and makes this method 
easier and more useful to work with.

Original comment by craig.skinfill on 23 Jan 2014 at 5:11

[GoogleCodeExporter]

Or with firstNonNull:

import static com.google.common.base.Objects.firstNonNull;
Enums.getIfPresent(MyEnum.class, firstNonNull(value, "SOME_DEFAULT_ENUM"))

Or with a ternary:

return ((value == null) ? Optional.<MyEnum>absent() : 
Enums.getIfPresent(MyEnum.class, value)).or(MyEnum.SOME_DEFAULT_ENUM);

Original comment by kak@google.com on 23 Jan 2014 at 6:14

[GoogleCodeExporter]

This issue has been migrated to GitHub.

It can be found at https://github.com/google/guava/issues/<issue id>

Original comment by cgdecker@google.com on 1 Nov 2014 at 4:10

• Added labels: MigratedToGitHub

[GoogleCodeExporter]

Original comment by cgdecker@google.com on 3 Nov 2014 at 9:07

• Added labels: Restrict-AddIssueComment-Commit