java.util.concurrent.atomic.AtomicMarkableReference
jdk1.6类 java.util.concurrent.atomic.AtomicMarkableReference
java.util.concurrent.atomic.AtomicMarkableReference
- private static class ReferenceBooleanPair<T>
- public AtomicMarkableReference(V initialRef, boolean initialMark)
- public V getReference()
- public boolean isMarked()
- public V get(boolean[] markHolder)
- public boolean weakCompareAndSet(V expectedReference, V newReference, boolean expectedMark, boolean newMark)
- public boolean compareAndSet(V expectedReference, V newReference, boolean expectedMark, boolean newMark)
- public void set(V newReference, boolean newMark)
- public boolean attemptMark(V expectedReference, boolean newMark)
/*
* %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 AtomicMarkableReference} maintains an object reference
* along with a mark bit, that can be updated atomically.
* <p>
* <p> Implementation note. This implementation maintains markable
* references by creating internal objects representing "boxed"
* [reference, boolean] pairs.
*
* @since 1.5
* @author Doug Lea
* @param <V> The type of object referred to by this reference
*/
/**
* AtomicMarkableReference 维护带有标记位的对象引用，可以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, boolean] 对的内部对象，此实现维持可标记的引用。
*/
public class AtomicMarkableReference<V> {
private static class ReferenceBooleanPair<T> {
private final T reference;
private final boolean bit;
ReferenceBooleanPair(T r, boolean i) {
reference = r; bit = i;
}
}
private final AtomicReference<ReferenceBooleanPair<V>> atomicRef;
/**
* Creates a new {@code AtomicMarkableReference} with the given
* initial values.
*
* @param initialRef the initial reference
* @param initialMark the initial mark
*/
/**
* 创建具有给定初始值的新 AtomicMarkableReference。
* @param initialRef 初始引用
* @param initialMark 初始标记
*/
public AtomicMarkableReference(V initialRef, boolean initialMark) {
atomicRef = new AtomicReference<ReferenceBooleanPair<V>> (new ReferenceBooleanPair<V>(initialRef, initialMark));
}
/**
* 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 mark.
*
* @return the current value of the mark
*/
/**
* 返回该标记的当前值。
* @return 该标记的当前值
*/
public boolean isMarked() {
return atomicRef.get().bit;
}
/**
* Returns the current values of both the reference and the mark.
* Typical usage is {@code boolean[1] holder; ref = v.get(holder); }.
*
* @param markHolder an array of size of at least one. On return,
* {@code markholder[0]} will hold the value of the mark.
* @return the current value of the reference
*/
/**
* 返回该引用和该标记的当前值。典型的用法为 boolean[1] holder; ref = v.get(holder); 。
* @param markHolder 大小至少为 1 的数组。返回时，markholder[0] 将保存该标记的值。
* @return 该引用的当前值
*/
public V get(boolean[] markHolder) {
ReferenceBooleanPair<V> p = atomicRef.get();
markHolder[0] = p.bit;
return p.reference;
}
/**
* Atomically sets the value of both the reference and mark
* to the given update values if the
* current reference is {@code ==} to the expected reference
* and the current mark is equal to the expected mark.
*
* <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 expectedMark the expected value of the mark
* @param newMark the new value for the mark
* @return true if successful
*/
/**
* 如果当前引用 == 预期引用，并且当前标记等于预期标记，那么以原子方式将引用和标记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 进行适当地选择。
* @param expectedReference 该引用的预期值
* @param newReference 该引用的新值
* @param expectedMark 该标记的预期值
* @param newMark 该标记的新值
* @return 如果成功，则返回 true
*/
public boolean weakCompareAndSet(V expectedReference,
V newReference,
boolean expectedMark,
boolean newMark) {
ReferenceBooleanPair<V> current = atomicRef.get();
return expectedReference == current.reference &&
expectedMark == current.bit &&
((newReference == current.reference && newMark == current.bit) ||
atomicRef.weakCompareAndSet(current,
new ReferenceBooleanPair<V>(newReference,
newMark)));
}
/**
* Atomically sets the value of both the reference and mark
* to the given update values if the
* current reference is {@code ==} to the expected reference
* and the current mark is equal to the expected mark.
*
* @param expectedReference the expected value of the reference
* @param newReference the new value for the reference
* @param expectedMark the expected value of the mark
* @param newMark the new value for the mark
* @return true if successful
*/
/**
* 如果当前引用 == 预期引用，并且当前标记等于预期标记，那么以原子方式将引用和标记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 expectedMark 该标记的预期值
* @param newMark 该标记的新值
* @return 如果成功，则返回 true
*/
public boolean compareAndSet(V expectedReference,
V newReference,
boolean expectedMark,
boolean newMark) {
ReferenceBooleanPair<V> current = atomicRef.get();
return expectedReference == current.reference &&
expectedMark == current.bit &&
((newReference == current.reference && newMark == current.bit) ||
atomicRef.compareAndSet(current,
new ReferenceBooleanPair<V>(newReference,
newMark)));
}
/**
* Unconditionally sets the value of both the reference and mark.
*
* @param newReference the new value for the reference
* @param newMark the new value for the mark
*/
/**
* 无条件地同时设置该引用和标记的值。
* @param newReference 该引用的新值
* @param newMark 该标记的新值
*/
public void set(V newReference, boolean newMark) {
ReferenceBooleanPair<V> current = atomicRef.get();
if (newReference != current.reference || newMark != current.bit)
atomicRef.set(new ReferenceBooleanPair<V>(newReference, newMark));
}
/**
* Atomically sets the value of the mark 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 newMark the new value for the mark
* @return true if successful
*/
/**
* 如果当前引用 == 预期引用，则以原子方式将该标记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 newMark 该标记的新值
* @return 如果成功，则返回 true
*/
public boolean attemptMark(V expectedReference, boolean newMark) {
ReferenceBooleanPair<V> current = atomicRef.get();
return expectedReference == current.reference &&
(newMark == current.bit ||
atomicRef.compareAndSet
(current, new ReferenceBooleanPair<V>(expectedReference,
newMark)));
}
}