http://findbugs.sourceforge.net/: Annotation the FindBugs tool supports 
package net.jcip.annotations;
import java.lang.annotation.*;

/*
 * Copyright (c) 2005 Brian Goetz and Tim Peierls
 * Released under the Creative Commons Attribution License
 *   (http://creativecommons.org/licenses/by/2.5)
 * Official home: http://www.jcip.net
 *
 * Any republication or derived work distributed in source code form
 * must include this copyright and license notice.
 */



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.RUNTIME)
public @interface NotThreadSafe {
}