com.github.phantomthief.pool.impl.CapacitySettableLinkedBlockingQueue Maven / Gradle / Ivy
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package com.github.phantomthief.pool.impl;
import java.io.Serializable;
import java.util.AbstractQueue;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.Consumer;
import java.util.function.Predicate;
/**
* 借鉴 RabbitMQ Java Client 从 {@link java.util.concurrent.LinkedBlockingQueue} 修改而来，有如下修改:
* 1. 增加 {@link #setCapacity(int)} 和 {@link #getCapacity()}
* 2. {@link #capacity} 判断边界从 == 改为 >=
* 3. 部分 signal() 信号触发改为 signalAll()
*
* 为什么不直接用 RabbitMQ 的版本？因为他们的版本有 bug，跑测试用例会在个别情况下把内部状态写坏，导致 NPE；
* CHECKSTYLE:OFF
*/
class CapacitySettableLinkedBlockingQueue extends AbstractQueue implements BlockingQueue, Serializable {
private static final long serialVersionUID = -6903933977591709194L;
/**
* Linked list node class.
*/
static class Node {
E item;
/**
* One of:
* - the real successor Node
* - this Node, meaning the successor is head.next
* - null, meaning there is no successor (this is the last node)
*/
Node next;
Node(E x) { item = x; }
}
/** The capacity bound, or Integer.MAX_VALUE if none */
private int capacity;
/** Current number of elements */
private final AtomicInteger count = new AtomicInteger();
/**
* Head of linked list.
* Invariant: head.item == null
*/
transient Node head;
/**
* Tail of linked list.
* Invariant: last.next == null
*/
private transient Node last;
/** Lock held by take, poll, etc */
private final ReentrantLock takeLock = new ReentrantLock();
/** Wait queue for waiting takes */
private final Condition notEmpty = takeLock.newCondition();
/** Lock held by put, offer, etc */
private final ReentrantLock putLock = new ReentrantLock();
/** Wait queue for waiting puts */
private final Condition notFull = putLock.newCondition();
/**
* Signals a waiting take. Called only from put/offer (which do not
* otherwise ordinarily lock takeLock.)
*/
private void signalNotEmpty() {
final ReentrantLock takeLock = this.takeLock;
takeLock.lock();
try {
notEmpty.signal();
} finally {
takeLock.unlock();
}
}
/**
* Signals a waiting put. Called only from take/poll.
*/
private void signalNotFull() {
final ReentrantLock putLock = this.putLock;
putLock.lock();
try {
notFull.signalAll();
} finally {
putLock.unlock();
}
}
/**
* Links node at end of queue.
*
* @param node the node
*/
private void enqueue(Node node) {
// assert putLock.isHeldByCurrentThread();
// assert last.next == null;
last = last.next = node;
}
/**
* Removes a node from head of queue.
*
* @return the node
*/
private E dequeue() {
// assert takeLock.isHeldByCurrentThread();
// assert head.item == null;
Node h = head;
Node first = h.next;
h.next = h; // help GC
head = first;
E x = first.item;
first.item = null;
return x;
}
/**
* Locks to prevent both puts and takes.
*/
void fullyLock() {
putLock.lock();
takeLock.lock();
}
/**
* Unlocks to allow both puts and takes.
*/
void fullyUnlock() {
takeLock.unlock();
putLock.unlock();
}
/**
* Creates a {@code LinkedBlockingQueue} with the given (fixed) capacity.
*
* @param capacity the capacity of this queue
* @throws IllegalArgumentException if {@code capacity} is not greater
* than zero
*/
public CapacitySettableLinkedBlockingQueue(int capacity) {
if (capacity <= 0) throw new IllegalArgumentException();
this.capacity = capacity;
last = head = new Node(null);
}
// this doc comment is overridden to remove the reference to collections
// greater in size than Integer.MAX_VALUE
/**
* Returns the number of elements in this queue.
*
* @return the number of elements in this queue
*/
public int size() {
return count.get();
}
/**
* Set a new capacity for the queue. Increasing the capacity can
* cause any waiting {@link #put(Object)} invocations to succeed if the new
* capacity is larger than the queue.
* @param capacity the new capacity for the queue
*/
public void setCapacity(int capacity) {
final int oldCapacity = this.capacity;
this.capacity = capacity;
final int size = count.get();
if (capacity > size && size >= oldCapacity) {
signalNotFull();
}
}
public int getCapacity() {
return capacity;
}
// this doc comment is a modified copy of the inherited doc comment,
// 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.
*
* Note that you cannot 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() {
return capacity - count.get();
}
/**
* Inserts the specified element at the tail of this queue, waiting if
* necessary for space to become available.
*
* @throws InterruptedException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public void put(E e) throws InterruptedException {
if (e == null) throw new NullPointerException();
final int c;
final Node
node = new Node(e);
final ReentrantLock putLock = this.putLock;
final AtomicInteger count = this.count;
putLock.lockInterruptibly();
try {
/*
* Note that count is used in wait guard even though it is
* not protected by lock. This works because count can
* only decrease at this point (all other puts are shut
* out by lock), and we (or some other waiting put) are
* signalled if it ever changes from capacity. Similarly
* for all other uses of count in other wait guards.
*/
while (count.get() >= capacity) {
notFull.await();
}
enqueue(node);
c = count.getAndIncrement();
if (c + 1 < capacity)
notFull.signal();
} finally {
putLock.unlock();
}
if (c == 0)
signalNotEmpty();
}
/**
* Inserts the specified element at the tail of this queue, waiting if
* necessary up to the specified wait time for space to become available.
*
* @return {@code true} if successful, or {@code false} if
* the specified waiting time elapses before space is available
* @throws InterruptedException {@inheritDoc}
* @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 int c;
final ReentrantLock putLock = this.putLock;
final AtomicInteger count = this.count;
putLock.lockInterruptibly();
try {
while (count.get() >= capacity) {
if (nanos <= 0L)
return false;
nanos = notFull.awaitNanos(nanos);
}
enqueue(new Node(e));
c = count.getAndIncrement();
if (c + 1 < capacity)
notFull.signal();
} finally {
putLock.unlock();
}
if (c == 0)
signalNotEmpty();
return true;
}
/**
* 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.
* When using a capacity-restricted queue, this method is generally
* preferable to method {@link BlockingQueue#add 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 AtomicInteger count = this.count;
if (count.get() >= capacity)
return false;
final int c;
final Node
node = new Node(e);
final ReentrantLock putLock = this.putLock;
putLock.lock();
try {
if (count.get() >= capacity)
return false;
enqueue(node);
c = count.getAndIncrement();
if (c + 1 < capacity)
notFull.signal();
} finally {
putLock.unlock();
}
if (c == 0)
signalNotEmpty();
return true;
}
public E take() throws InterruptedException {
final E x;
final int c;
final AtomicInteger count = this.count;
final ReentrantLock takeLock = this.takeLock;
takeLock.lockInterruptibly();
try {
while (count.get() == 0) {
notEmpty.await();
}
x = dequeue();
c = count.getAndDecrement();
if (c > 1)
notEmpty.signal();
} finally {
takeLock.unlock();
}
if (c >= capacity)
signalNotFull();
return x;
}
public E poll(long timeout, TimeUnit unit) throws InterruptedException {
final E x;
final int c;
long nanos = unit.toNanos(timeout);
final AtomicInteger count = this.count;
final ReentrantLock takeLock = this.takeLock;
takeLock.lockInterruptibly();
try {
while (count.get() == 0) {
if (nanos <= 0L)
return null;
nanos = notEmpty.awaitNanos(nanos);
}
x = dequeue();
c = count.getAndDecrement();
if (c > 1)
notEmpty.signal();
} finally {
takeLock.unlock();
}
if (c >= capacity)
signalNotFull();
return x;
}
public E poll() {
final AtomicInteger count = this.count;
if (count.get() == 0)
return null;
final E x;
final int c;
final ReentrantLock takeLock = this.takeLock;
takeLock.lock();
try {
if (count.get() == 0)
return null;
x = dequeue();
c = count.getAndDecrement();
if (c > 1)
notEmpty.signal();
} finally {
takeLock.unlock();
}
if (c >= capacity)
signalNotFull();
return x;
}
public E peek() {
final AtomicInteger count = this.count;
if (count.get() == 0)
return null;
final ReentrantLock takeLock = this.takeLock;
takeLock.lock();
try {
return (count.get() > 0) ? head.next.item : null;
} finally {
takeLock.unlock();
}
}
/**
* Unlinks interior Node p with predecessor pred.
*/
void unlink(
Node p, Node pred) {
// assert putLock.isHeldByCurrentThread();
// assert takeLock.isHeldByCurrentThread();
// p.next is not changed, to allow iterators that are
// traversing p to maintain their weak-consistency guarantee.
p.item = null;
pred.next = p.next;
if (last == p)
last = pred;
if (count.getAndDecrement() >= capacity)
notFull.signalAll();
}
/**
* 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).
*
* @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;
fullyLock();
try {
for (Node pred = head, p = pred.next;
p != null;
pred = p, p = p.next) {
if (o.equals(p.item)) {
unlink(p, pred);
return true;
}
}
return false;
} finally {
fullyUnlock();
}
}
/**
* 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;
fullyLock();
try {
for (Node p = head.next; p != null; p = p.next)
if (o.equals(p.item))
return true;
return false;
} finally {
fullyUnlock();
}
}
/**
* Returns an array containing all of the elements in this queue, in
* proper sequence.
*
* The returned array will be "safe" in that no references to it are
* maintained by this queue. (In other words, this method must allocate
* a new array). The caller is thus free to modify the returned array.
*
*
This method acts as bridge between array-based and collection-based
* APIs.
*
* @return an array containing all of the elements in this queue
*/
public Object[] toArray() {
fullyLock();
try {
int size = count.get();
Object[] a = new Object[size];
int k = 0;
for (Node p = head.next; p != null; p = p.next)
a[k++] = p.item;
return a;
} finally {
fullyUnlock();
}
}
/**
* Returns an array containing all of the elements in this queue, in
* proper sequence; the runtime type of the returned array is that of
* the specified array. If the queue fits in the specified array, it
* is returned therein. Otherwise, a new array is allocated with the
* runtime type of the specified array and the size of this queue.
*
* 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}.
*
*
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.
*
*
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}:
*
*
{@code String[] y = x.toArray(new String[0]);}
*
* 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
* @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[] toArray(T[] a) {
fullyLock();
try {
int size = count.get();
if (a.length < size)
a = (T[])java.lang.reflect.Array.newInstance
(a.getClass().getComponentType(), size);
int k = 0;
for (Node p = head.next; p != null; p = p.next)
a[k++] = (T)p.item;
if (a.length > k)
a[k] = null;
return a;
} finally {
fullyUnlock();
}
}
/**
* Atomically removes all of the elements from this queue.
* The queue will be empty after this call returns.
*/
public void clear() {
fullyLock();
try {
for (Node p, h = head; (p = h.next) != null; h = p) {
h.next = h;
p.item = null;
}
head = last;
// assert head.item == null && head.next == null;
if (count.getAndSet(0) >= capacity)
notFull.signalAll();
} finally {
fullyUnlock();
}
}
/**
* @throws UnsupportedOperationException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
*/
public int drainTo(Collection c) {
return drainTo(c, Integer.MAX_VALUE);
}
/**
* @throws UnsupportedOperationException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
*/
public int drainTo(Collection c, int maxElements) {
Objects.requireNonNull(c);
if (c == this)
throw new IllegalArgumentException();
if (maxElements <= 0)
return 0;
boolean signalNotFull = false;
final ReentrantLock takeLock = this.takeLock;
takeLock.lock();
try {
int n = Math.min(maxElements, count.get());
// count.get provides visibility to first n Nodes
Node h = head;
int i = 0;
try {
while (i < n) {
Node p = h.next;
c.add(p.item);
p.item = null;
h.next = h;
h = p;
++i;
}
return n;
} finally {
// Restore invariants even if c.add() threw
if (i > 0) {
// assert h.item == null;
head = h;
signalNotFull = (count.getAndAdd(-i) >= capacity);
}
}
} finally {
takeLock.unlock();
if (signalNotFull)
signalNotFull();
}
}
/**
* Used for any element traversal that is not entirely under lock.
* Such traversals must handle both:
* - dequeued nodes (p.next == p)
* - (possibly multiple) interior removed nodes (p.item == null)
*/
Node succ(Node p) {
if (p == (p = p.next))
p = head.next;
return p;
}
/**
* 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).
*
* The returned iterator is
* weakly consistent.
*
* @return an iterator over the elements in this queue in proper sequence
*/
public Iterator iterator() {
return new Itr();
}
/**
* Weakly-consistent iterator.
*
* Lazily updated ancestor field provides expected O(1) remove(),
* but still O(n) in the worst case, whenever the saved ancestor
* is concurrently deleted.
*/
private class Itr implements Iterator {
private Node next; // Node holding nextItem
private E nextItem; // next item to hand out
private Node lastRet;
private Node ancestor; // Helps unlink lastRet on remove()
Itr() {
fullyLock();
try {
if ((next = head.next) != null)
nextItem = next.item;
} finally {
fullyUnlock();
}
}
public boolean hasNext() {
return next != null;
}
public E next() {
Node p;
if ((p = next) == null)
throw new NoSuchElementException();
lastRet = p;
E x = nextItem;
fullyLock();
try {
E e = null;
for (p = p.next; p != null && (e = p.item) == null; )
p = succ(p);
next = p;
nextItem = e;
} finally {
fullyUnlock();
}
return x;
}
public void forEachRemaining(Consumer action) {
// A variant of forEachFrom
Objects.requireNonNull(action);
Node p;
if ((p = next) == null) return;
lastRet = p;
next = null;
final int batchSize = 64;
Object[] es = null;
int n, len = 1;
do {
fullyLock();
try {
if (es == null) {
p = p.next;
for (Node q = p; q != null; q = succ(q))
if (q.item != null && ++len == batchSize)
break;
es = new Object[len];
es[0] = nextItem;
nextItem = null;
n = 1;
} else
n = 0;
for (; p != null && n < len; p = succ(p))
if ((es[n] = p.item) != null) {
lastRet = p;
n++;
}
} finally {
fullyUnlock();
}
for (int i = 0; i < n; i++) {
@SuppressWarnings("unchecked") E e = (E) es[i];
action.accept(e);
}
} while (n > 0 && p != null);
}
public void remove() {
Node p = lastRet;
if (p == null)
throw new IllegalStateException();
lastRet = null;
fullyLock();
try {
if (p.item != null) {
if (ancestor == null)
ancestor = head;
ancestor = findPred(p, ancestor);
unlink(p, ancestor);
}
} finally {
fullyUnlock();
}
}
}
/**
* A customized variant of Spliterators.IteratorSpliterator.
* Keep this class in sync with (very similar) LBDSpliterator.
*/
private final class LBQSpliterator implements Spliterator {
static final int MAX_BATCH = 1 << 25; // max batch array size;
Node current; // current node; null until initialized
int batch; // batch size for splits
boolean exhausted; // true when no more nodes
long est = size(); // size estimate
LBQSpliterator() {}
public long estimateSize() { return est; }
public Spliterator trySplit() {
Node h;
if (!exhausted &&
((h = current) != null || (h = head.next) != null)
&& h.next != null) {
int n = batch = Math.min(batch + 1, MAX_BATCH);
Object[] a = new Object[n];
int i = 0;
Node p = current;
fullyLock();
try {
if (p != null || (p = head.next) != null)
for (; p != null && i < n; p = succ(p))
if ((a[i] = p.item) != null)
i++;
} finally {
fullyUnlock();
}
if ((current = p) == null) {
est = 0L;
exhausted = true;
}
else if ((est -= i) < 0L)
est = 0L;
if (i > 0)
return Spliterators.spliterator
(a, 0, i, (Spliterator.ORDERED |
Spliterator.NONNULL |
Spliterator.CONCURRENT));
}
return null;
}
public boolean tryAdvance(Consumer action) {
Objects.requireNonNull(action);
if (!exhausted) {
E e = null;
fullyLock();
try {
Node p;
if ((p = current) != null || (p = head.next) != null)
do {
e = p.item;
p = succ(p);
} while (e == null && p != null);
if ((current = p) == null)
exhausted = true;
} finally {
fullyUnlock();
}
if (e != null) {
action.accept(e);
return true;
}
}
return false;
}
public void forEachRemaining(Consumer action) {
Objects.requireNonNull(action);
if (!exhausted) {
exhausted = true;
Node p = current;
current = null;
forEachFrom(action, p);
}
}
public int characteristics() {
return (Spliterator.ORDERED |
Spliterator.NONNULL |
Spliterator.CONCURRENT);
}
}
/**
* Returns a {@link Spliterator} over the elements in this queue.
*
* The returned spliterator is
* weakly consistent.
*
*
The {@code Spliterator} reports {@link Spliterator#CONCURRENT},
* {@link Spliterator#ORDERED}, and {@link Spliterator#NONNULL}.
*
* @implNote
* The {@code Spliterator} implements {@code trySplit} to permit limited
* parallelism.
*
* @return a {@code Spliterator} over the elements in this queue
* @since 1.8
*/
public Spliterator spliterator() {
return new LBQSpliterator();
}
/**
* @throws NullPointerException {@inheritDoc}
*/
public void forEach(Consumer action) {
Objects.requireNonNull(action);
forEachFrom(action, null);
}
/**
* Runs action on each element found during a traversal starting at p.
* If p is null, traversal starts at head.
*/
void forEachFrom(Consumer action, Node p) {
// Extract batches of elements while holding the lock; then
// run the action on the elements while not
final int batchSize = 64; // max number of elements per batch
Object[] es = null; // container for batch of elements
int n, len = 0;
do {
fullyLock();
try {
if (es == null) {
if (p == null) p = head.next;
for (Node q = p; q != null; q = succ(q))
if (q.item != null && ++len == batchSize)
break;
es = new Object[len];
}
for (n = 0; p != null && n < len; p = succ(p))
if ((es[n] = p.item) != null)
n++;
} finally {
fullyUnlock();
}
for (int i = 0; i < n; i++) {
@SuppressWarnings("unchecked") E e = (E) es[i];
action.accept(e);
}
} while (n > 0 && p != null);
}
/**
* @throws NullPointerException {@inheritDoc}
*/
public boolean removeIf(Predicate filter) {
Objects.requireNonNull(filter);
return bulkRemove(filter);
}
/**
* @throws NullPointerException {@inheritDoc}
*/
public boolean removeAll(Collection c) {
Objects.requireNonNull(c);
return bulkRemove(e -> c.contains(e));
}
/**
* @throws NullPointerException {@inheritDoc}
*/
public boolean retainAll(Collection c) {
Objects.requireNonNull(c);
return bulkRemove(e -> !c.contains(e));
}
/**
* Returns the predecessor of live node p, given a node that was
* once a live ancestor of p (or head); allows unlinking of p.
*/
Node findPred(
Node p, Node ancestor) {
// assert p.item != null;
if (ancestor.item == null)
ancestor = head;
// Fails with NPE if precondition not satisfied
for (Node q; (q = ancestor.next) != p; )
ancestor = q;
return ancestor;
}
/** Implementation of bulk remove methods. */
@SuppressWarnings("unchecked")
private boolean bulkRemove(Predicate filter) {
boolean removed = false;
Node p = null, ancestor = head;
Node[] nodes = null;
int n, len = 0;
do {
// 1. Extract batch of up to 64 elements while holding the lock.
fullyLock();
try {
if (nodes == null) { // first batch; initialize
p = head.next;
for (Node q = p; q != null; q = succ(q))
if (q.item != null && ++len == 64)
break;
nodes = (Node[]) new Node[len];
}
for (n = 0; p != null && n < len; p = succ(p))
nodes[n++] = p;
} finally {
fullyUnlock();
}
// 2. Run the filter on the elements while lock is free.
long deathRow = 0L; // "bitset" of size 64
for (int i = 0; i < n; i++) {
final E e;
if ((e = nodes[i].item) != null && filter.test(e))
deathRow |= 1L << i;
}
// 3. Remove any filtered elements while holding the lock.
if (deathRow != 0) {
fullyLock();
try {
for (int i = 0; i < n; i++) {
final Node q;
if ((deathRow & (1L << i)) != 0L
&& (q = nodes[i]).item != null) {
ancestor = findPred(q, ancestor);
unlink(q, ancestor);
removed = true;
}
nodes[i] = null; // help GC
}
} finally {
fullyUnlock();
}
}
} while (n > 0 && p != null);
return removed;
}
/**
* Saves this queue to a stream (that is, serializes it).
*
* @param s the stream
* @throws java.io.IOException if an I/O error occurs
* @serialData The capacity is emitted (int), followed by all of
* its elements (each an {@code Object}) in the proper order,
* followed by a null
*/
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
fullyLock();
try {
// Write out any hidden stuff, plus capacity
s.defaultWriteObject();
// Write out all elements in the proper order.
for (Node p = head.next; p != null; p = p.next)
s.writeObject(p.item);
// Use trailing null as sentinel
s.writeObject(null);
} finally {
fullyUnlock();
}
}
/**
* Reconstitutes this queue from a stream (that is, deserializes it).
* @param s the stream
* @throws ClassNotFoundException if the class of a serialized object
* could not be found
* @throws java.io.IOException if an I/O error occurs
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// Read in capacity, and any hidden stuff
s.defaultReadObject();
count.set(0);
last = head = new Node(null);
// Read in all elements and place in queue
for (;;) {
@SuppressWarnings("unchecked")
E item = (E)s.readObject();
if (item == null)
break;
add(item);
}
}
}
// CHECKSTYLE:ON