You need to include a jar that this class exists in. You can find it here

If using Maven, you can add the following dependency declaration:

<dependency>
  <groupId>com.google.code.findbugs</groupId>
  <artifactId>jsr305</artifactId>
  <version>3.0.2</version>
</dependency>

and for Gradle:

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

The artifact has been moved from net.sourceforge.findbugs to

<dependency>
    <groupId>com.google.code.findbugs</groupId>
    <artifactId>jsr305</artifactId>
    <version>3.0.0</version>
</dependency>

If you are using Gradle, you could include the dependency like this:

repositories {
    mavenCentral()
}

dependencies {
    compile group: 'com.google.code.findbugs', name: 'jsr305', version: '3.0.0'
}