java.util.concurrent.atomic.AtomicStampedReference
jdk1.6类 java.util.concurrent.atomic.AtomicStampedReference
java.util.concurrent.atomic.AtomicStampedReference
- public AtomicStampedReference(V initialRef, int initialStamp)
- public V getReference()
- public int getStamp()
- public V get(int[] stampHolder)
- public boolean weakCompareAndSet(V expectedReference, V newReference, int expectedStamp, int newStamp)
- public boolean compareAndSet(V expectedReference, V newReference, int expectedStamp, int newStamp)
- public void set(V newReference, int newStamp)
- public boolean attemptStamp(V expectedReference, int newStamp)
/*
* %W% %E%
*
* Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util.concurrent.atomic;
/**
* An {@code AtomicStampedReference} maintains an object reference
* along with an integer "stamp", that can be updated atomically.
*
* <p> Implementation note. This implementation maintains stamped
* references by creating internal objects representing "boxed"
* [reference, integer] pairs.
*
* @since 1.5
* @author Doug Lea
* @param <V> The type of object referred to by this reference
*/
/**
* AtomicStampedReference 维护带有整数“标志”的对象引用，可以用原子方式对其进行更新。
* 实现注意事项。通过创建表示“已装箱”的 [reference, integer] 对的内部对象，此实现维持带标志的引用。
*/
public class AtomicStampedReference<V> {
private static class ReferenceIntegerPair<T> {
private final T reference;
private final int integer;
ReferenceIntegerPair(T r, int i) {
reference = r; integer = i;
}
}
private final AtomicReference<ReferenceIntegerPair<V>> atomicRef;
/**
* Creates a new {@code AtomicStampedReference} with the given
* initial values.
*
* @param initialRef the initial reference
* @param initialStamp the initial stamp
*/
/**
* 创建具有给定初始值的新 AtomicStampedReference。
* @param initialRef 初始引用
* @param initialStamp 初始标志
*/
public AtomicStampedReference(V initialRef, int initialStamp) {
atomicRef = new AtomicReference<ReferenceIntegerPair<V>>
(new ReferenceIntegerPair<V>(initialRef, initialStamp));
}
/**
* Returns the current value of the reference.
*
* @return the current value of the reference
*/
/**
* 返回该引用的当前值。
* @return 该引用的当前值
*/
public V getReference() {
return atomicRef.get().reference;
}
/**
* Returns the current value of the stamp.
*
* @return the current value of the stamp
*/
/**
* 返回该标志的当前值。
* @return 该标志的当前值
*/
public int getStamp() {
return atomicRef.get().integer;
}
/**
* Returns the current values of both the reference and the stamp.
* Typical usage is {@code int[1] holder; ref = v.get(holder); }.
*
* @param stampHolder an array of size of at least one. On return,
* {@code stampholder[0]} will hold the value of the stamp.
* @return the current value of the reference
*/
/**
* 返回该引用和该标志的当前值。典型的用法为 int[1] holder; ref = v.get(holder); 。
* @param stampHolder 大小至少为 1 的数组。返回时，stampholder[0] 将保存该标志的值。
* @return 该引用的当前值
*/
public V get(int[] stampHolder) {
ReferenceIntegerPair<V> p = atomicRef.get();
stampHolder[0] = p.integer;
return p.reference;
}
/**
* Atomically sets the value of both the reference and stamp
* to the given update values if the
* current reference is {@code ==} to the expected reference
* and the current stamp is equal to the expected stamp.
*
* <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 expectedReference the expected value of the reference
* @param newReference the new value for the reference
* @param expectedStamp the expected value of the stamp
* @param newStamp the new value for the stamp
* @return true if successful
*/
/**
* 如果当前引用 == 预期引用，并且当前标志等于预期标志，
* 则以原子方式将该引用和该标志的值设置为给定的更新值。可能意外失败并且不提供排序保证，
* 所以只有在很少的情况下才对 compareAndSet 进行适当的选择。
* @param expectedReference 该引用的预期值
* @param newReference 该引用的新值
* @param expectedStamp 该标志的预期值
* @param newStamp 该标志的新值
* @return 如果成功，则返回 true
*/
public boolean weakCompareAndSet(V expectedReference,
V newReference,
int expectedStamp,
int newStamp) {
ReferenceIntegerPair<V> current = atomicRef.get();
return expectedReference == current.reference &&
expectedStamp == current.integer &&
((newReference == current.reference &&
newStamp == current.integer) ||
atomicRef.weakCompareAndSet(current,
new ReferenceIntegerPair<V>(newReference,
newStamp)));
}
/**
* Atomically sets the value of both the reference and stamp
* to the given update values if the
* current reference is {@code ==} to the expected reference
* and the current stamp is equal to the expected stamp.
*
* @param expectedReference the expected value of the reference
* @param newReference the new value for the reference
* @param expectedStamp the expected value of the stamp
* @param newStamp the new value for the stamp
* @return true if successful
*/
/**
* 如果当前引用 == 预期引用，并且当前标志等于预期标志，则以原子方式将该引用和该标志的值设置为给定的更新值。
* @param expectedReference 该引用的预期值
* @param newReference 该引用的新值
* @param expectedStamp 该标志的预期值
* @param newStamp 该标志的新值
* @return 如果成功，则返回 true
*/
public boolean compareAndSet(V expectedReference,
V newReference,
int expectedStamp,
int newStamp) {
ReferenceIntegerPair<V> current = atomicRef.get();
return expectedReference == current.reference &&
expectedStamp == current.integer &&
((newReference == current.reference &&
newStamp == current.integer) ||
atomicRef.compareAndSet(current,
new ReferenceIntegerPair<V>(newReference,
newStamp)));
}
/**
* Unconditionally sets the value of both the reference and stamp.
*
* @param newReference the new value for the reference
* @param newStamp the new value for the stamp
*/
/**
* 无条件地同时设置该引用和标志的值。
* @param newReference 该引用的新值
* @param newStamp 该标志的新值
*/
public void set(V newReference, int newStamp) {
ReferenceIntegerPair<V> current = atomicRef.get();
if (newReference != current.reference || newStamp != current.integer)
atomicRef.set(new ReferenceIntegerPair<V>(newReference, newStamp));
}
/**
* Atomically sets the value of the stamp to the given update value
* if the current reference is {@code ==} to the expected
* reference. Any given invocation of this operation may fail
* (return {@code false}) spuriously, but repeated invocation
* when the current value holds the expected value and no other
* thread is also attempting to set the value will eventually
* succeed.
*
* @param expectedReference the expected value of the reference
* @param newStamp the new value for the stamp
* @return true if successful
*/
/**
* 如果当前引用 == 预期引用，则以原子方式将该标志的值设置为给定的更新值。
* 此操作的任何给定调用都可能会意外失败（返回 false），
* 但是在当前值保持预期值而且没有其他线程也在尝试设置该值时，重复调用将最终获得成功。
* @param expectedReference 该引用的预期值
* @param newStamp 该标志的新值
* @return 如果成功，则返回 true
*/
public boolean attemptStamp(V expectedReference, int newStamp) {
ReferenceIntegerPair<V> current = atomicRef.get();
return expectedReference == current.reference &&
(newStamp == current.integer ||
atomicRef.compareAndSet(current,
new ReferenceIntegerPair<V>(expectedReference,
newStamp)));
}
}