Exception to throw when instance variables are null

Question

I'm working on making a codebase complaint with a list of PMD rules. These include that you're not allowed to throw or catch NullPointerExceptions. I found this method which requires 2 instance variables to be non-null in order to run. It throws a NullPointerException otherwise:

public String build() {
if (apiKey == null || url == null) {
    throw new NullPointerException(
            "Cannot build: API key and URL must be set");
}

What should it be throwing instead? it seems to me that NullPointerException would be the bast call. The only other thing that comes to mind is IllegalArgumentException, but these aren't really arguments, so I don't think it really fits.

Jon Skeet · Accepted Answer · 2014-03-18 15:00:37Z

7

IllegalStateException seems entirely appropriate here:

Signals that a method has been invoked at an illegal or inappropriate time.

That describes the situation reasonably clearly, doesn't it?

answered Mar 18, 2014 at 15:00

Jon Skeet

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Tim B · Accepted Answer · 2014-03-18 15:00:49Z

6

IllegalStateException springs to mind.

One thing to consider here is whether this should be a checked or an unchecked exception. You could also consider making your own explicit Exception for this case if it can usefully be handled differently from the generic IllegalStateException.

answered Mar 18, 2014 at 15:00

Tim B

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2 Comments

Paul Vargas Over a year ago

+1 Although Jon Skeet beat you by 10 seconds. I'll be good to you.

Tim B Over a year ago

@PaulVargas Yeah, but it's Jon Skeet. Even Chuck Norris can't get an answer in before Jon Skeet: meta.stackexchange.com/questions/9134/jon-skeet-facts

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