http://findbugs.sourceforge.net/: JSR305 Annotations for Findbugs 
package javax.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

import javax.annotation.meta.TypeQualifierNickname;
import javax.annotation.meta.When;


The annotated element might be null, and uses of the element should check for null.


When this annotation is applied to a method it applies to the method return value.

/**
 * The annotated element might be null, and uses of the element should check for null.
 * <p>
 * When this annotation is applied to a method it applies to the method return value.
 */
@Documented
@TypeQualifierNickname
@Nonnull(when = When.MAYBE)
@Retention(RetentionPolicy.RUNTIME)
public @interface CheckForNull {

}