http://findbugs.sourceforge.net/: JSR305 Annotations for Findbugs 
/*
 * Copyright (c) 2005 Brian Goetz
 * Released under the Creative Commons Attribution License
 *   (http://creativecommons.org/licenses/by/2.5)
 * Official home: http://www.jcip.net
 */
package javax.annotation.concurrent;

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


The class to which this annotation is applied is not thread-safe. This
annotation primarily exists for clarifying the non-thread-safety of a class
that might otherwise be assumed to be thread-safe, despite the fact that it
is a bad idea to assume a class is thread-safe without good reason.

See Also:
  • ThreadSafe
/**
 * The class to which this annotation is applied is not thread-safe. This
 * annotation primarily exists for clarifying the non-thread-safety of a class
 * that might otherwise be assumed to be thread-safe, despite the fact that it
 * is a bad idea to assume a class is thread-safe without good reason.
 * 
 * @see ThreadSafe
 */
@Documented
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.CLASS)
public @interface NotThreadSafe {
}