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 thread-safe.  This means that
no sequences of accesses (reads and writes to public fields, calls to public methods)
may put the object into an invalid state, regardless of the interleaving of those actions
by the runtime, and without requiring any additional synchronization or coordination on the
part of the caller.

/**
 * The class to which this annotation is applied is thread-safe.  This means that
 * no sequences of accesses (reads and writes to public fields, calls to public methods)
 * may put the object into an invalid state, regardless of the interleaving of those actions
 * by the runtime, and without requiring any additional synchronization or coordination on the
 * part of the caller.
 */
@Documented
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface ThreadSafe {
}