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

Answer 1

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'
    // ...
}

Answer 2

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.