Comments on: How to Avoid NullPointerExceptions (NPE)?

By: Maniganda Prakash

Maniganda Prakash — Wed, 29 Dec 2010 13:31:59 +0000

It must be “if(!result.isEmpty())” instead of “if(result.isEmpty())” (Andre had already pointed it out)

By: Act Like a Senior Developer | Test Server

Act Like a Senior Developer | Test Server — Sat, 12 Jun 2010 03:05:00 +0000

[...] more information on this topic, please read my other post about null pointer [...]

By: Isa Goksu

Isa Goksu — Sat, 10 Apr 2010 17:54:31 +0000

In that case, I’d recommend using NullObjectPattern. You’d have User domain model. You extend this model with UnknownUser. An in any case of exception you can easily return new UnknownUser which doesn’t have any property set. You workflow would continue without any problem. You don’t have to check anything. Then again if you would like to have a business logic around users that are not in DB, then u can check this by “if user instanceof UnknownUser” kinda statement and put your business logic there.

By: Sunil

Sunil — Sat, 10 Apr 2010 13:21:54 +0000

Thanks a lot.This is really useful.One question though

"throw UserNotFoundException("No user found with guid: %1$s", guid); // or any ServiceException you like.."

If I want to continue after this exception is thrown wouldn't I need to handle with an if and else loop? What do you think will be a better approach to handle such cases?

By: Lexandro weblogja » NPE

Lexandro weblogja » NPE — Mon, 15 Mar 2010 23:27:32 +0000

[...] olvasgattam egy érdekes cikket a null pointer exception elkerüléséről, ahol a srác felvázolt pár elképzelést [...]

By: Isa Goksu

Isa Goksu — Fri, 27 Nov 2009 18:03:11 +0000

@cease, in that case I'd not prefer both, the best would be NullUser :) However early UserNotFound exception is still more meaningful than trying to figure out how come it became null later in the code.

@andre 10x for correcting

By: André

André — Fri, 27 Nov 2009 13:54:40 +0000

I guess it should be “if (!result.isEmpty())” instead of “if (result.isEmpty())” in your examples.

By: Act Like a Senior Developer – About Clean Code

Act Like a Senior Developer – About Clean Code — Wed, 25 Nov 2009 19:03:48 +0000

[...] more information on this topic, please read my other post about null pointer [...]

By: cease

cease — Wed, 25 Nov 2009 18:55:55 +0000

what about the case you’re querying for an object of type User (for example) and it doesn’t exist, do you throw exception or return null… I would prefer the null check than a checked exception, returning new User makes no sense in this case. thoughts ?

By: Isa Goksu

Isa Goksu — Tue, 12 May 2009 17:30:36 +0000

@mike If you have a situation that your service users might add elements to the returning collection (as in API/framework development, or any open source library development), then I’d definitely say “Yes, you should return an empty array list”. Then again, generally Service/DAO clients don’t add anything new to the returning collection as far as I concern. To me if you’re adding a new element to the result set by yourself, there is something smelling in that code, instead they might try using double brace initialization to do their custom stuff. And even though they might get UnsupportedOperationException, I think it’s still meaningful than NPE :) At least this time you know where exactly the problem is, right ;)