src/share/classes/java/util/concurrent/ArrayBlockingQueue.java
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*** 47,64 ****
* operations obtain elements at the head of the queue.
*
* <p>This is a classic "bounded buffer", in which a
* fixed-sized array holds elements inserted by producers and
* extracted by consumers. Once created, the capacity cannot be
! * increased. Attempts to <tt>put</tt> an element into a full queue
! * will result in the operation blocking; attempts to <tt>take</tt> an
* element from an empty queue will similarly block.
*
! * <p> This class supports an optional fairness policy for ordering
* waiting producer and consumer threads. By default, this ordering
* is not guaranteed. However, a queue constructed with fairness set
! * to <tt>true</tt> grants threads access in FIFO order. Fairness
* generally decreases throughput but reduces variability and avoids
* starvation.
*
* <p>This class and its iterator implement all of the
* <em>optional</em> methods of the {@link Collection} and {@link
--- 47,64 ----
* operations obtain elements at the head of the queue.
*
* <p>This is a classic "bounded buffer", in which a
* fixed-sized array holds elements inserted by producers and
* extracted by consumers. Once created, the capacity cannot be
! * changed. Attempts to {@code put} an element into a full queue
! * will result in the operation blocking; attempts to {@code take} an
* element from an empty queue will similarly block.
*
! * <p>This class supports an optional fairness policy for ordering
* waiting producer and consumer threads. By default, this ordering
* is not guaranteed. However, a queue constructed with fairness set
! * to {@code true} grants threads access in FIFO order. Fairness
* generally decreases throughput but reduces variability and avoids
* starvation.
*
* <p>This class and its iterator implement all of the
* <em>optional</em> methods of the {@link Collection} and {@link
*** 82,106 ****
* necessary here.
*/
private static final long serialVersionUID = -817911632652898426L;
/** The queued items */
! private final E[] items;
! /** items index for next take, poll or remove */
! private int takeIndex;
! /** items index for next put, offer, or add. */
! private int putIndex;
! /** Number of items in the queue */
! private int count;
/*
* Concurrency control uses the classic two-condition algorithm
* found in any textbook.
*/
/** Main lock guarding all access */
! private final ReentrantLock lock;
/** Condition for waiting takes */
private final Condition notEmpty;
/** Condition for waiting puts */
private final Condition notFull;
--- 82,109 ----
* necessary here.
*/
private static final long serialVersionUID = -817911632652898426L;
/** The queued items */
! final Object[] items;
+ /** items index for next take, poll, peek or remove */
+ int takeIndex;
+
+ /** items index for next put, offer, or add */
+ int putIndex;
+
+ /** Number of elements in the queue */
+ int count;
+
/*
* Concurrency control uses the classic two-condition algorithm
* found in any textbook.
*/
/** Main lock guarding all access */
! final ReentrantLock lock;
/** Condition for waiting takes */
private final Condition notEmpty;
/** Condition for waiting puts */
private final Condition notFull;
*** 108,121 ****
/**
* Circularly increment i.
*/
final int inc(int i) {
! return (++i == items.length)? 0 : i;
}
/**
* Inserts element at current put position, advances, and signals.
* Call only when holding lock.
*/
private void insert(E x) {
items[putIndex] = x;
--- 111,153 ----
/**
* Circularly increment i.
*/
final int inc(int i) {
! return (++i == items.length) ? 0 : i;
}
/**
+ * Circularly decrement i.
+ */
+ final int dec(int i) {
+ return ((i == 0) ? items.length : i) - 1;
+ }
+
+ @SuppressWarnings("unchecked")
+ static <E> E cast(Object item) {
+ return (E) item;
+ }
+
+ /**
+ * Returns item at index i.
+ */
+ final E itemAt(int i) {
+ return this.<E>cast(items[i]);
+ }
+
+ /**
+ * Throws NullPointerException if argument is null.
+ *
+ * @param v the element
+ */
+ private static void checkNotNull(Object v) {
+ if (v == null)
+ throw new NullPointerException();
+ }
+
+ /**
* Inserts element at current put position, advances, and signals.
* Call only when holding lock.
*/
private void insert(E x) {
items[putIndex] = x;
*** 127,151 ****
/**
* Extracts element at current take position, advances, and signals.
* Call only when holding lock.
*/
private E extract() {
! final E[] items = this.items;
! E x = items[takeIndex];
items[takeIndex] = null;
takeIndex = inc(takeIndex);
--count;
notFull.signal();
return x;
}
/**
! * Utility for remove and iterator.remove: Delete item at position i.
* Call only when holding lock.
*/
void removeAt(int i) {
! final E[] items = this.items;
// if removing front item, just advance
if (i == takeIndex) {
items[takeIndex] = null;
takeIndex = inc(takeIndex);
} else {
--- 159,184 ----
/**
* Extracts element at current take position, advances, and signals.
* Call only when holding lock.
*/
private E extract() {
! final Object[] items = this.items;
! E x = this.<E>cast(items[takeIndex]);
items[takeIndex] = null;
takeIndex = inc(takeIndex);
--count;
notFull.signal();
return x;
}
/**
! * Deletes item at position i.
! * Utility for remove and iterator.remove.
* Call only when holding lock.
*/
void removeAt(int i) {
! final Object[] items = this.items;
// if removing front item, just advance
if (i == takeIndex) {
items[takeIndex] = null;
takeIndex = inc(takeIndex);
} else {
*** 165,237 ****
--count;
notFull.signal();
}
/**
! * Creates an <tt>ArrayBlockingQueue</tt> with the given (fixed)
* capacity and default access policy.
*
* @param capacity the capacity of this queue
! * @throws IllegalArgumentException if <tt>capacity</tt> is less than 1
*/
public ArrayBlockingQueue(int capacity) {
this(capacity, false);
}
/**
! * Creates an <tt>ArrayBlockingQueue</tt> with the given (fixed)
* capacity and the specified access policy.
*
* @param capacity the capacity of this queue
! * @param fair if <tt>true</tt> then queue accesses for threads blocked
* on insertion or removal, are processed in FIFO order;
! * if <tt>false</tt> the access order is unspecified.
! * @throws IllegalArgumentException if <tt>capacity</tt> is less than 1
*/
public ArrayBlockingQueue(int capacity, boolean fair) {
if (capacity <= 0)
throw new IllegalArgumentException();
! this.items = (E[]) new Object[capacity];
lock = new ReentrantLock(fair);
notEmpty = lock.newCondition();
notFull = lock.newCondition();
}
/**
! * Creates an <tt>ArrayBlockingQueue</tt> with the given (fixed)
* capacity, the specified access policy and initially containing the
* elements of the given collection,
* added in traversal order of the collection's iterator.
*
* @param capacity the capacity of this queue
! * @param fair if <tt>true</tt> then queue accesses for threads blocked
* on insertion or removal, are processed in FIFO order;
! * if <tt>false</tt> the access order is unspecified.
* @param c the collection of elements to initially contain
! * @throws IllegalArgumentException if <tt>capacity</tt> is less than
! * <tt>c.size()</tt>, or less than 1.
* @throws NullPointerException if the specified collection or any
* of its elements are null
*/
public ArrayBlockingQueue(int capacity, boolean fair,
Collection<? extends E> c) {
this(capacity, fair);
- if (capacity < c.size())
- throw new IllegalArgumentException();
! for (E e : c)
! add(e);
}
/**
* Inserts the specified element at the tail of this queue if it is
* possible to do so immediately without exceeding the queue's capacity,
! * returning <tt>true</tt> upon success and throwing an
! * <tt>IllegalStateException</tt> if this queue is full.
*
* @param e the element to add
! * @return <tt>true</tt> (as specified by {@link Collection#add})
* @throws IllegalStateException if this queue is full
* @throws NullPointerException if the specified element is null
*/
public boolean add(E e) {
return super.add(e);
--- 198,283 ----
--count;
notFull.signal();
}
/**
! * Creates an {@code ArrayBlockingQueue} with the given (fixed)
* capacity and default access policy.
*
* @param capacity the capacity of this queue
! * @throws IllegalArgumentException if {@code capacity < 1}
*/
public ArrayBlockingQueue(int capacity) {
this(capacity, false);
}
/**
! * Creates an {@code ArrayBlockingQueue} with the given (fixed)
* capacity and the specified access policy.
*
* @param capacity the capacity of this queue
! * @param fair if {@code true} then queue accesses for threads blocked
* on insertion or removal, are processed in FIFO order;
! * if {@code false} the access order is unspecified.
! * @throws IllegalArgumentException if {@code capacity < 1}
*/
public ArrayBlockingQueue(int capacity, boolean fair) {
if (capacity <= 0)
throw new IllegalArgumentException();
! this.items = new Object[capacity];
lock = new ReentrantLock(fair);
notEmpty = lock.newCondition();
notFull = lock.newCondition();
}
/**
! * Creates an {@code ArrayBlockingQueue} with the given (fixed)
* capacity, the specified access policy and initially containing the
* elements of the given collection,
* added in traversal order of the collection's iterator.
*
* @param capacity the capacity of this queue
! * @param fair if {@code true} then queue accesses for threads blocked
* on insertion or removal, are processed in FIFO order;
! * if {@code false} the access order is unspecified.
* @param c the collection of elements to initially contain
! * @throws IllegalArgumentException if {@code capacity} is less than
! * {@code c.size()}, or less than 1.
* @throws NullPointerException if the specified collection or any
* of its elements are null
*/
public ArrayBlockingQueue(int capacity, boolean fair,
Collection<? extends E> c) {
this(capacity, fair);
! final ReentrantLock lock = this.lock;
! lock.lock(); // Lock only for visibility, not mutual exclusion
! try {
! int i = 0;
! try {
! for (E e : c) {
! checkNotNull(e);
! items[i++] = e;
}
+ } catch (ArrayIndexOutOfBoundsException ex) {
+ throw new IllegalArgumentException();
+ }
+ count = i;
+ putIndex = (i == capacity) ? 0 : i;
+ } finally {
+ lock.unlock();
+ }
+ }
/**
* Inserts the specified element at the tail of this queue if it is
* possible to do so immediately without exceeding the queue's capacity,
! * returning {@code true} upon success and throwing an
! * {@code IllegalStateException} if this queue is full.
*
* @param e the element to add
! * @return {@code true} (as specified by {@link Collection#add})
* @throws IllegalStateException if this queue is full
* @throws NullPointerException if the specified element is null
*/
public boolean add(E e) {
return super.add(e);
*** 238,255 ****
}
/**
* Inserts the specified element at the tail of this queue if it is
* possible to do so immediately without exceeding the queue's capacity,
! * returning <tt>true</tt> upon success and <tt>false</tt> if this queue
* is full. This method is generally preferable to method {@link #add},
* which can fail to insert an element only by throwing an exception.
*
* @throws NullPointerException if the specified element is null
*/
public boolean offer(E e) {
! if (e == null) throw new NullPointerException();
final ReentrantLock lock = this.lock;
lock.lock();
try {
if (count == items.length)
return false;
--- 284,301 ----
}
/**
* Inserts the specified element at the tail of this queue if it is
* possible to do so immediately without exceeding the queue's capacity,
! * returning {@code true} upon success and {@code false} if this queue
* is full. This method is generally preferable to method {@link #add},
* which can fail to insert an element only by throwing an exception.
*
* @throws NullPointerException if the specified element is null
*/
public boolean offer(E e) {
! checkNotNull(e);
final ReentrantLock lock = this.lock;
lock.lock();
try {
if (count == items.length)
return false;
*** 268,289 ****
*
* @throws InterruptedException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public void put(E e) throws InterruptedException {
! if (e == null) throw new NullPointerException();
! final E[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
- try {
while (count == items.length)
notFull.await();
- } catch (InterruptedException ie) {
- notFull.signal(); // propagate to non-interrupted thread
- throw ie;
- }
insert(e);
} finally {
lock.unlock();
}
}
--- 314,329 ----
*
* @throws InterruptedException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public void put(E e) throws InterruptedException {
! checkNotNull(e);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
while (count == items.length)
notFull.await();
insert(e);
} finally {
lock.unlock();
}
}
*** 297,356 ****
* @throws NullPointerException {@inheritDoc}
*/
public boolean offer(E e, long timeout, TimeUnit unit)
throws InterruptedException {
! if (e == null) throw new NullPointerException();
long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
! for (;;) {
! if (count != items.length) {
! insert(e);
! return true;
! }
if (nanos <= 0)
return false;
- try {
nanos = notFull.awaitNanos(nanos);
- } catch (InterruptedException ie) {
- notFull.signal(); // propagate to non-interrupted thread
- throw ie;
}
! }
} finally {
lock.unlock();
}
}
public E poll() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
! if (count == 0)
! return null;
! E x = extract();
! return x;
} finally {
lock.unlock();
}
}
public E take() throws InterruptedException {
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
- try {
while (count == 0)
notEmpty.await();
! } catch (InterruptedException ie) {
! notEmpty.signal(); // propagate to non-interrupted thread
! throw ie;
! }
! E x = extract();
! return x;
} finally {
lock.unlock();
}
}
--- 337,380 ----
* @throws NullPointerException {@inheritDoc}
*/
public boolean offer(E e, long timeout, TimeUnit unit)
throws InterruptedException {
! checkNotNull(e);
long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
! while (count == items.length) {
if (nanos <= 0)
return false;
nanos = notFull.awaitNanos(nanos);
}
! insert(e);
! return true;
} finally {
lock.unlock();
}
}
public E poll() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
! return (count == 0) ? null : extract();
} finally {
lock.unlock();
}
}
public E take() throws InterruptedException {
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
while (count == 0)
notEmpty.await();
! return extract();
} finally {
lock.unlock();
}
}
*** 357,391 ****
public E poll(long timeout, TimeUnit unit) throws InterruptedException {
long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
! for (;;) {
! if (count != 0) {
! E x = extract();
! return x;
! }
if (nanos <= 0)
return null;
- try {
nanos = notEmpty.awaitNanos(nanos);
- } catch (InterruptedException ie) {
- notEmpty.signal(); // propagate to non-interrupted thread
- throw ie;
}
!
! }
} finally {
lock.unlock();
}
}
public E peek() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
! return (count == 0) ? null : items[takeIndex];
} finally {
lock.unlock();
}
}
--- 381,406 ----
public E poll(long timeout, TimeUnit unit) throws InterruptedException {
long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
! while (count == 0) {
if (nanos <= 0)
return null;
nanos = notEmpty.awaitNanos(nanos);
}
! return extract();
} finally {
lock.unlock();
}
}
public E peek() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
! return (count == 0) ? null : itemAt(takeIndex);
} finally {
lock.unlock();
}
}
*** 410,423 ****
// without the reference to unlimited queues.
/**
* Returns the number of additional elements that this queue can ideally
* (in the absence of memory or resource constraints) accept without
* blocking. This is always equal to the initial capacity of this queue
! * less the current <tt>size</tt> of this queue.
*
* <p>Note that you <em>cannot</em> always tell if an attempt to insert
! * an element will succeed by inspecting <tt>remainingCapacity</tt>
* because it may be the case that another thread is about to
* insert or remove an element.
*/
public int remainingCapacity() {
final ReentrantLock lock = this.lock;
--- 425,438 ----
// without the reference to unlimited queues.
/**
* Returns the number of additional elements that this queue can ideally
* (in the absence of memory or resource constraints) accept without
* blocking. This is always equal to the initial capacity of this queue
! * less the current {@code size} of this queue.
*
* <p>Note that you <em>cannot</em> always tell if an attempt to insert
! * an element will succeed by inspecting {@code remainingCapacity}
* because it may be the case that another thread is about to
* insert or remove an element.
*/
public int remainingCapacity() {
final ReentrantLock lock = this.lock;
*** 429,491 ****
}
}
/**
* Removes a single instance of the specified element from this queue,
! * if it is present. More formally, removes an element <tt>e</tt> such
! * that <tt>o.equals(e)</tt>, if this queue contains one or more such
* elements.
! * Returns <tt>true</tt> if this queue contained the specified element
* (or equivalently, if this queue changed as a result of the call).
*
* @param o element to be removed from this queue, if present
! * @return <tt>true</tt> if this queue changed as a result of the call
*/
public boolean remove(Object o) {
if (o == null) return false;
! final E[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
! int i = takeIndex;
! int k = 0;
! for (;;) {
! if (k++ >= count)
! return false;
if (o.equals(items[i])) {
removeAt(i);
return true;
}
- i = inc(i);
}
!
} finally {
lock.unlock();
}
}
/**
! * Returns <tt>true</tt> if this queue contains the specified element.
! * More formally, returns <tt>true</tt> if and only if this queue contains
! * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
*
* @param o object to be checked for containment in this queue
! * @return <tt>true</tt> if this queue contains the specified element
*/
public boolean contains(Object o) {
if (o == null) return false;
! final E[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
! int i = takeIndex;
! int k = 0;
! while (k++ < count) {
if (o.equals(items[i]))
return true;
- i = inc(i);
- }
return false;
} finally {
lock.unlock();
}
}
--- 444,503 ----
}
}
/**
* Removes a single instance of the specified element from this queue,
! * if it is present. More formally, removes an element {@code e} such
! * that {@code o.equals(e)}, if this queue contains one or more such
* elements.
! * Returns {@code true} if this queue contained the specified element
* (or equivalently, if this queue changed as a result of the call).
*
+ * <p>Removal of interior elements in circular array based queues
+ * is an intrinsically slow and disruptive operation, so should
+ * be undertaken only in exceptional circumstances, ideally
+ * only when the queue is known not to be accessible by other
+ * threads.
+ *
* @param o element to be removed from this queue, if present
! * @return {@code true} if this queue changed as a result of the call
*/
public boolean remove(Object o) {
if (o == null) return false;
! final Object[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
! for (int i = takeIndex, k = count; k > 0; i = inc(i), k--) {
if (o.equals(items[i])) {
removeAt(i);
return true;
}
}
! return false;
} finally {
lock.unlock();
}
}
/**
! * Returns {@code true} if this queue contains the specified element.
! * More formally, returns {@code true} if and only if this queue contains
! * at least one element {@code e} such that {@code o.equals(e)}.
*
* @param o object to be checked for containment in this queue
! * @return {@code true} if this queue contains the specified element
*/
public boolean contains(Object o) {
if (o == null) return false;
! final Object[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
! for (int i = takeIndex, k = count; k > 0; i = inc(i), k--)
if (o.equals(items[i]))
return true;
return false;
} finally {
lock.unlock();
}
}
*** 502,522 ****
* APIs.
*
* @return an array containing all of the elements in this queue
*/
public Object[] toArray() {
! final E[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
Object[] a = new Object[count];
! int k = 0;
! int i = takeIndex;
! while (k < count) {
! a[k++] = items[i];
! i = inc(i);
! }
return a;
} finally {
lock.unlock();
}
}
--- 514,531 ----
* APIs.
*
* @return an array containing all of the elements in this queue
*/
public Object[] toArray() {
! final Object[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
+ final int count = this.count;
Object[] a = new Object[count];
! for (int i = takeIndex, k = 0; k < count; i = inc(i), k++)
! a[k] = items[i];
return a;
} finally {
lock.unlock();
}
}
*** 529,554 ****
* runtime type of the specified array and the size of this queue.
*
* <p>If this queue fits in the specified array with room to spare
* (i.e., the array has more elements than this queue), the element in
* the array immediately following the end of the queue is set to
! * <tt>null</tt>.
*
* <p>Like the {@link #toArray()} method, this method acts as bridge between
* array-based and collection-based APIs. Further, this method allows
* precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs.
*
! * <p>Suppose <tt>x</tt> is a queue known to contain only strings.
* The following code can be used to dump the queue into a newly
! * allocated array of <tt>String</tt>:
*
* <pre>
* String[] y = x.toArray(new String[0]);</pre>
*
! * Note that <tt>toArray(new Object[0])</tt> is identical in function to
! * <tt>toArray()</tt>.
*
* @param a the array into which the elements of the queue are to
* be stored, if it is big enough; otherwise, a new array of the
* same runtime type is allocated for this purpose
* @return an array containing all of the elements in this queue
--- 538,563 ----
* runtime type of the specified array and the size of this queue.
*
* <p>If this queue fits in the specified array with room to spare
* (i.e., the array has more elements than this queue), the element in
* the array immediately following the end of the queue is set to
! * {@code null}.
*
* <p>Like the {@link #toArray()} method, this method acts as bridge between
* array-based and collection-based APIs. Further, this method allows
* precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs.
*
! * <p>Suppose {@code x} is a queue known to contain only strings.
* The following code can be used to dump the queue into a newly
! * allocated array of {@code String}:
*
* <pre>
* String[] y = x.toArray(new String[0]);</pre>
*
! * Note that {@code toArray(new Object[0])} is identical in function to
! * {@code toArray()}.
*
* @param a the array into which the elements of the queue are to
* be stored, if it is big enough; otherwise, a new array of the
* same runtime type is allocated for this purpose
* @return an array containing all of the elements in this queue
*** 555,582 ****
* @throws ArrayStoreException if the runtime type of the specified array
* is not a supertype of the runtime type of every element in
* this queue
* @throws NullPointerException if the specified array is null
*/
public <T> T[] toArray(T[] a) {
! final E[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
! if (a.length < count)
a = (T[])java.lang.reflect.Array.newInstance(
! a.getClass().getComponentType(),
! count
! );
!
! int k = 0;
! int i = takeIndex;
! while (k < count) {
! a[k++] = (T)items[i];
! i = inc(i);
! }
! if (a.length > count)
a[count] = null;
return a;
} finally {
lock.unlock();
}
--- 564,587 ----
* @throws ArrayStoreException if the runtime type of the specified array
* is not a supertype of the runtime type of every element in
* this queue
* @throws NullPointerException if the specified array is null
*/
+ @SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) {
! final Object[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
! final int count = this.count;
! final int len = a.length;
! if (len < count)
a = (T[])java.lang.reflect.Array.newInstance(
! a.getClass().getComponentType(), count);
! for (int i = takeIndex, k = 0; k < count; i = inc(i), k++)
! a[k] = (T) items[i];
! if (len > count)
a[count] = null;
return a;
} finally {
lock.unlock();
}
*** 584,594 ****
public String toString() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
! return super.toString();
} finally {
lock.unlock();
}
}
--- 589,611 ----
public String toString() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
! int k = count;
! if (k == 0)
! return "[]";
!
! StringBuilder sb = new StringBuilder();
! sb.append('[');
! for (int i = takeIndex; ; i = inc(i)) {
! Object e = items[i];
! sb.append(e == this ? "(this Collection)" : e);
! if (--k == 0)
! return sb.append(']').toString();
! sb.append(',').append(' ');
! }
} finally {
lock.unlock();
}
}
*** 595,614 ****
/**
* Atomically removes all of the elements from this queue.
* The queue will be empty after this call returns.
*/
public void clear() {
! final E[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
! int i = takeIndex;
! int k = count;
! while (k-- > 0) {
items[i] = null;
- i = inc(i);
- }
count = 0;
putIndex = 0;
takeIndex = 0;
notFull.signalAll();
} finally {
--- 612,627 ----
/**
* Atomically removes all of the elements from this queue.
* The queue will be empty after this call returns.
*/
public void clear() {
! final Object[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
! for (int i = takeIndex, k = count; k > 0; i = inc(i), k--)
items[i] = null;
count = 0;
putIndex = 0;
takeIndex = 0;
notFull.signalAll();
} finally {
*** 621,643 ****
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
*/
public int drainTo(Collection<? super E> c) {
! if (c == null)
! throw new NullPointerException();
if (c == this)
throw new IllegalArgumentException();
! final E[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
int i = takeIndex;
int n = 0;
int max = count;
while (n < max) {
! c.add(items[i]);
items[i] = null;
i = inc(i);
++n;
}
if (n > 0) {
--- 634,655 ----
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
*/
public int drainTo(Collection<? super E> c) {
! checkNotNull(c);
if (c == this)
throw new IllegalArgumentException();
! final Object[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
int i = takeIndex;
int n = 0;
int max = count;
while (n < max) {
! c.add(this.<E>cast(items[i]));
items[i] = null;
i = inc(i);
++n;
}
if (n > 0) {
*** 657,682 ****
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
*/
public int drainTo(Collection<? super E> c, int maxElements) {
! if (c == null)
! throw new NullPointerException();
if (c == this)
throw new IllegalArgumentException();
if (maxElements <= 0)
return 0;
! final E[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
int i = takeIndex;
int n = 0;
! int sz = count;
! int max = (maxElements < count)? maxElements : count;
while (n < max) {
! c.add(items[i]);
items[i] = null;
i = inc(i);
++n;
}
if (n > 0) {
--- 669,692 ----
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
*/
public int drainTo(Collection<? super E> c, int maxElements) {
! checkNotNull(c);
if (c == this)
throw new IllegalArgumentException();
if (maxElements <= 0)
return 0;
! final Object[] items = this.items;
final ReentrantLock lock = this.lock;
lock.lock();
try {
int i = takeIndex;
int n = 0;
! int max = (maxElements < count) ? maxElements : count;
while (n < max) {
! c.add(this.<E>cast(items[i]));
items[i] = null;
i = inc(i);
++n;
}
if (n > 0) {
*** 688,786 ****
} finally {
lock.unlock();
}
}
-
/**
* Returns an iterator over the elements in this queue in proper sequence.
! * The returned <tt>Iterator</tt> is a "weakly consistent" iterator that
! * will never throw {@link ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to)
* reflect any modifications subsequent to construction.
*
* @return an iterator over the elements in this queue in proper sequence
*/
public Iterator<E> iterator() {
- final ReentrantLock lock = this.lock;
- lock.lock();
- try {
return new Itr();
- } finally {
- lock.unlock();
}
- }
/**
! * Iterator for ArrayBlockingQueue
*/
private class Itr implements Iterator<E> {
! /**
! * Index of element to be returned by next,
! * or a negative number if no such.
! */
! private int nextIndex;
- /**
- * nextItem holds on to item fields because once we claim
- * that an element exists in hasNext(), we must return it in
- * the following next() call even if it was in the process of
- * being removed when hasNext() was called.
- */
- private E nextItem;
-
- /**
- * Index of element returned by most recent call to next.
- * Reset to -1 if this element is deleted by a call to remove.
- */
- private int lastRet;
-
Itr() {
lastRet = -1;
! if (count == 0)
! nextIndex = -1;
! else {
! nextIndex = takeIndex;
! nextItem = items[takeIndex];
}
}
public boolean hasNext() {
! /*
! * No sync. We can return true by mistake here
! * only if this iterator passed across threads,
! * which we don't support anyway.
! */
! return nextIndex >= 0;
}
- /**
- * Checks whether nextIndex is valid; if so setting nextItem.
- * Stops iterator when either hits putIndex or sees null item.
- */
- private void checkNext() {
- if (nextIndex == putIndex) {
- nextIndex = -1;
- nextItem = null;
- } else {
- nextItem = items[nextIndex];
- if (nextItem == null)
- nextIndex = -1;
- }
- }
-
public E next() {
final ReentrantLock lock = ArrayBlockingQueue.this.lock;
lock.lock();
try {
! if (nextIndex < 0)
throw new NoSuchElementException();
lastRet = nextIndex;
! E x = nextItem;
! nextIndex = inc(nextIndex);
! checkNext();
return x;
} finally {
lock.unlock();
}
}
--- 698,780 ----
} finally {
lock.unlock();
}
}
/**
* Returns an iterator over the elements in this queue in proper sequence.
! * The elements will be returned in order from first (head) to last (tail).
! *
! * <p>The returned {@code Iterator} is a "weakly consistent" iterator that
! * will never throw {@link java.util.ConcurrentModificationException
! * ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to)
* reflect any modifications subsequent to construction.
*
* @return an iterator over the elements in this queue in proper sequence
*/
public Iterator<E> iterator() {
return new Itr();
}
/**
! * Iterator for ArrayBlockingQueue. To maintain weak consistency
! * with respect to puts and takes, we (1) read ahead one slot, so
! * as to not report hasNext true but then not have an element to
! * return -- however we later recheck this slot to use the most
! * current value; (2) ensure that each array slot is traversed at
! * most once (by tracking "remaining" elements); (3) skip over
! * null slots, which can occur if takes race ahead of iterators.
! * However, for circular array-based queues, we cannot rely on any
! * well established definition of what it means to be weakly
! * consistent with respect to interior removes since these may
! * require slot overwrites in the process of sliding elements to
! * cover gaps. So we settle for resiliency, operating on
! * established apparent nexts, which may miss some elements that
! * have moved between calls to next.
*/
private class Itr implements Iterator<E> {
! private int remaining; // Number of elements yet to be returned
! private int nextIndex; // Index of element to be returned by next
! private E nextItem; // Element to be returned by next call to next
! private E lastItem; // Element returned by last call to next
! private int lastRet; // Index of last element returned, or -1 if none
Itr() {
+ final ReentrantLock lock = ArrayBlockingQueue.this.lock;
+ lock.lock();
+ try {
lastRet = -1;
! if ((remaining = count) > 0)
! nextItem = itemAt(nextIndex = takeIndex);
! } finally {
! lock.unlock();
}
}
public boolean hasNext() {
! return remaining > 0;
}
public E next() {
final ReentrantLock lock = ArrayBlockingQueue.this.lock;
lock.lock();
try {
! if (remaining <= 0)
throw new NoSuchElementException();
lastRet = nextIndex;
! E x = itemAt(nextIndex); // check for fresher value
! if (x == null) {
! x = nextItem; // we are forced to report old value
! lastItem = null; // but ensure remove fails
! }
! else
! lastItem = x;
! while (--remaining > 0 && // skip over nulls
! (nextItem = itemAt(nextIndex = inc(nextIndex))) == null)
! ;
return x;
} finally {
lock.unlock();
}
}
*** 791,807 ****
try {
int i = lastRet;
if (i == -1)
throw new IllegalStateException();
lastRet = -1;
!
! int ti = takeIndex;
removeAt(i);
! // back up cursor (reset to front if was first element)
! nextIndex = (i == ti) ? takeIndex : i;
! checkNext();
} finally {
lock.unlock();
}
}
}
}
--- 785,805 ----
try {
int i = lastRet;
if (i == -1)
throw new IllegalStateException();
lastRet = -1;
! E x = lastItem;
! lastItem = null;
! // only remove if item still at index
! if (x != null && x == items[i]) {
! boolean removingHead = (i == takeIndex);
removeAt(i);
! if (!removingHead)
! nextIndex = dec(nextIndex);
! }
} finally {
lock.unlock();
}
}
}
+
}