How can I make IntelliJ IDEA understand my null-checking method?
intellij-idea, java, nullable
Solution
I don't believe there's any way to resolve the warning with the code written as it is. I was hoping to find that IntelliJ supports a value for `@SuppressWarnings` that you could use on the `useObject(x)` statement, but according to this source it does not. You may just have to bite the bullet and change your code to something like the following:
if (x != null && !isBlank(x)) {
useObject(x);
}
Notice that I renamed the method `isNull` to `isBlank` since it is my understanding that the actual method you're calling that does the check for `null` checks other conditions as well.
Problem
I have a method where a parameter is marked with the `@Nonnull` annotation. The code which calls the method has to check whether the value is null. Rather than just a straight `x != null` check, it is calling a utility method on another class. (In the real code, the utility method also checks whether it is a blank String). My problem is that Intellij Idea is showing an inspection warning on the Nonnull method call, saying that my variable "might be null". I know it cannot be null because of the utility method check - how can I tell the inspector that? Since that is a bit abstract, here's a minimal example of what I mean: ``` package org.ethelred.ideatest; import javax.annotation.CheckForNull; import javax.annotation.Nonnull; /** * tests annotations */ public class AnnotationChecker { public static void main(String[] args) { String x = null; if(args.length > 0) { x = args[0]; } if(!isNull(x)) { useObject(x); } if(x != null) { useObject(x); } } public static boolean isNull(@CheckForNull Object o) { return o == null; } public static void useObject(@Nonnull Object o) { System.out.println(o); } } ``` This uses the JSR 305 annotations. In this example, in the first call to `useObject` Intellij puts a warning on the `x` parameter saying "Argument 'x' might be null". In the second call, there is no warning.