--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicReference.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,155 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent.atomic;
+import sun.misc.Unsafe;
+
+/**
+ * An object reference that may be updated atomically. See the {@link
+ * java.util.concurrent.atomic} package specification for description
+ * of the properties of atomic variables.
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> The type of object referred to by this reference
+ */
+public class AtomicReference<V>  implements java.io.Serializable {
+    private static final long serialVersionUID = -1848883965231344442L;
+
+    private static final Unsafe unsafe = Unsafe.getUnsafe();
+    private static final long valueOffset;
+
+    static {
+      try {
+        valueOffset = unsafe.objectFieldOffset
+            (AtomicReference.class.getDeclaredField("value"));
+      } catch (Exception ex) { throw new Error(ex); }
+    }
+
+    private volatile V value;
+
+    /**
+     * Creates a new AtomicReference with the given initial value.
+     *
+     * @param initialValue the initial value
+     */
+    public AtomicReference(V initialValue) {
+        value = initialValue;
+    }
+
+    /**
+     * Creates a new AtomicReference with null initial value.
+     */
+    public AtomicReference() {
+    }
+
+    /**
+     * Gets the current value.
+     *
+     * @return the current value
+     */
+    public final V get() {
+        return value;
+    }
+
+    /**
+     * Sets to the given value.
+     *
+     * @param newValue the new value
+     */
+    public final void set(V newValue) {
+        value = newValue;
+    }
+
+    /**
+     * Eventually sets to the given value.
+     *
+     * @param newValue the new value
+     * @since 1.6
+     */
+    public final void lazySet(V newValue) {
+        unsafe.putOrderedObject(this, valueOffset, newValue);
+    }
+
+    /**
+     * Atomically sets the value to the given updated value
+     * if the current value {@code ==} the expected value.
+     * @param expect the expected value
+     * @param update the new value
+     * @return true if successful. False return indicates that
+     * the actual value was not equal to the expected value.
+     */
+    public final boolean compareAndSet(V expect, V update) {
+        return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
+    }
+
+    /**
+     * Atomically sets the value to the given updated value
+     * if the current value {@code ==} the expected value.
+     *
+     * <p>May <a href="package-summary.html#Spurious">fail spuriously</a>
+     * and does not provide ordering guarantees, so is only rarely an
+     * appropriate alternative to {@code compareAndSet}.
+     *
+     * @param expect the expected value
+     * @param update the new value
+     * @return true if successful.
+     */
+    public final boolean weakCompareAndSet(V expect, V update) {
+        return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
+    }
+
+    /**
+     * Atomically sets to the given value and returns the old value.
+     *
+     * @param newValue the new value
+     * @return the previous value
+     */
+    public final V getAndSet(V newValue) {
+        while (true) {
+            V x = get();
+            if (compareAndSet(x, newValue))
+                return x;
+        }
+    }
+
+    /**
+     * Returns the String representation of the current value.
+     * @return the String representation of the current value.
+     */
+    public String toString() {
+        return String.valueOf(get());
+    }
+
+}