How do I get @ParametersAreNonnullByDefault to work?

Question

I've made several attempts at getting package annotation @ParametersAreNonnullByDefault to work for me in a maven project but with no success. Could someone share a link to a minimal/sample maven project where this is setup (or post the pom.xml and package-info.java and demo class)?

I'm talking about having findbugs processor enforce it for me.

Answer 1

How to apply @ParametersAreNonnullByDefault

Create a file package-info.java in your package where you want to enforce the desired behavior.

In that file, do the following:

/**  * You should do it like this!  */ @ParametersAreNonnullByDefault package com.stackoverflow;  import javax.annotation.ParametersAreNonnullByDefault; 

How not to apply @ParametersAreNonnullByDefault

Don't do the following in a Java source file:

/**  * But you shouldn't do it this way!  */ @ParametersAreNonnullByDefault package com.stackoverflow;  import javax.annotation.ParametersAreNonnullByDefault;  public class Answer { ... 

Declaring annotations like this is ambiguous.

Notes

It would be OK to apply the annotation directly on Answer class.

package com.stackoverflow;  import javax.annotation.ParametersAreNonnullByDefault;  /**  * You can do it like this also.  */ @ParametersAreNonnullByDefault public class Answer { ... 

The exact same things apply to @ParametersAreNullableByDefault also.

Answer 2

For Android projects (for example when using libraries like Retrofit etc), this is the dependency to put in app/build.gradle (as mentioned by @Saket):

dependencies {
    implementation 'com.google.code.findbugs:jsr305:3.0.2'
    // ...
}