| /* |
| * 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. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.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/publicdomain/zero/1.0/ |
| */ |
| |
| /** |
| * A small toolkit of classes that support lock-free thread-safe |
| * programming on single variables. Instances of Atomic classes |
| * maintain values that are accessed and updated using methods |
| * otherwise available for fields using associated atomic {@link |
| * java.lang.invoke.VarHandle} operations. |
| * |
| * <p>Instances of classes |
| * {@link java.util.concurrent.atomic.AtomicBoolean}, |
| * {@link java.util.concurrent.atomic.AtomicInteger}, |
| * {@link java.util.concurrent.atomic.AtomicLong}, and |
| * {@link java.util.concurrent.atomic.AtomicReference} |
| * each provide access and updates to a single variable of the |
| * corresponding type. Each class also provides appropriate utility |
| * methods for that type. For example, classes {@code AtomicLong} and |
| * {@code AtomicInteger} provide atomic increment methods. One |
| * application is to generate sequence numbers, as in: |
| * |
| * <pre> {@code |
| * class Sequencer { |
| * private final AtomicLong sequenceNumber |
| * = new AtomicLong(0); |
| * public long next() { |
| * return sequenceNumber.getAndIncrement(); |
| * } |
| * }}</pre> |
| * |
| * <p>Arbitrary transformations of the contained value are provided both |
| * by low-level read-modify-write operations such as {@code compareAndSet} |
| * and by higher-level methods such as {@code getAndUpdate}. |
| * |
| * <p>These classes are not general purpose replacements for {@code |
| * java.lang.Integer} and related classes. They do <em>not</em> |
| * define methods such as {@code equals}, {@code hashCode} and {@code |
| * compareTo}. Because atomic variables are expected to be mutated, |
| * they are poor choices for hash table keys. |
| * |
| * <p>The |
| * {@link java.util.concurrent.atomic.AtomicIntegerArray}, |
| * {@link java.util.concurrent.atomic.AtomicLongArray}, and |
| * {@link java.util.concurrent.atomic.AtomicReferenceArray} classes |
| * further extend atomic operation support to arrays of these types. |
| * These classes are also notable in providing {@code volatile} access |
| * semantics for their array elements. |
| * |
| * <p>In addition to classes representing single values and arrays, |
| * this package contains <em>Updater</em> classes that can be used to |
| * obtain {@code compareAndSet} and related operations on any selected |
| * {@code volatile} field of any selected class. These classes |
| * predate the introduction of {@link |
| * java.lang.invoke.VarHandle}, and are of more limited use. |
| * {@link java.util.concurrent.atomic.AtomicReferenceFieldUpdater}, |
| * {@link java.util.concurrent.atomic.AtomicIntegerFieldUpdater}, and |
| * {@link java.util.concurrent.atomic.AtomicLongFieldUpdater} are |
| * reflection-based utilities that provide access to the associated |
| * field types. These are mainly of use in atomic data structures in |
| * which several {@code volatile} fields of the same node (for |
| * example, the links of a tree node) are independently subject to |
| * atomic updates. These classes enable greater flexibility in how |
| * and when to use atomic updates, at the expense of more awkward |
| * reflection-based setup, less convenient usage, and weaker |
| * guarantees. |
| * |
| * <p>The {@link java.util.concurrent.atomic.AtomicMarkableReference} |
| * class associates a single boolean with a reference. For example, this |
| * bit might be used inside a data structure to mean that the object |
| * being referenced has logically been deleted. |
| * |
| * The {@link java.util.concurrent.atomic.AtomicStampedReference} |
| * class associates an integer value with a reference. This may be |
| * used for example, to represent version numbers corresponding to |
| * series of updates. |
| * |
| * @since 1.5 |
| */ |
| package java.util.concurrent.atomic; |
