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/*
This is not an official specification document, and usage is restricted.


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(c) 2005-2007 Sun Microsystems, Inc. All Rights Reserved.

Neither this file nor any files generated from it describe a complete
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example, no permission is given for you to incorporate this file, in
whole or in part, in an implementation of a Java specification.

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documentation, such as a unified set of documents of API signatures for
a platform that includes technologies expressed as Java APIs. The file
may also be used to produce "compilation stubs," which allow
applications to be compiled and validated for such platforms.

Any work generated from this file, such as unified javadocs or compiled
stub files, must be accompanied by this notice in its entirety.

This work corresponds to the API signatures of JSR 219: Foundation
Profile 1.1. In the event of a discrepency between this work and the
JSR 219 specification, which is available at
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*/


  


package java.lang;

import java.lang.ref.*;

/** 
 * This class extends ThreadLocal to provide inheritance of values
 * from parent thread to child thread: when a child thread is created, the
 * child receives initial values for all inheritable thread-local variables
 * for which the parent has values.  Normally the child's values will be
 * identical to the parent's; however, the child's value can be made an
 * arbitrary function of the parent's by overriding the childValue
 * method in this class.
 * 
 * 
Inheritable thread-local variables are used in preference to
 * ordinary thread-local variables when the per-thread-attribute being
 * maintained in the variable (e.g., User ID, Transaction ID) must be
 * automatically transmitted to any child threads that are created.
 *
 * @author  Josh Bloch and Doug Lea
 * @version 1.17, 03/12/05
 * @see     ThreadLocal
 * @since   1.2
 */
public class InheritableThreadLocal extends java.lang.ThreadLocal
{

    public InheritableThreadLocal() { }

    /** 
     * Computes the child's initial value for this inheritable thread-local
     * variable as a function of the parent's value at the time the child
     * thread is created.  This method is called from within the parent
     * thread before the child is started.
     * 
     * This method merely returns its input argument, and should be overridden
     * if a different behavior is desired.
     *
     * @param parentValue the parent thread's value
     * @return the child thread's initial value
     */
    protected java.lang.Object childValue(java.lang.Object parentValue) {
        return null;
    }
}