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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain. Use, modify, and |
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* redistribute this code in any way without acknowledgement. |
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*/ |
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|
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|
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package java.util.concurrent; |
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import java.util.concurrent.locks.*; |
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import java.util.*; |
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|
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/** |
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* An unbounded queue of <tt>Delayed</tt> elements, in which |
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* elements can only be taken when their delay has expired. |
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* @since 1.5 |
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* @author Doug Lea |
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*/ |
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|
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public class DelayQueue<E extends Delayed> extends AbstractQueue<E> |
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implements BlockingQueue<E> { |
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|
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private transient final ReentrantLock lock = new ReentrantLock(); |
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private transient final Condition available = lock.newCondition(); |
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private final PriorityQueue<E> q = new PriorityQueue<E>(); |
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|
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/** |
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* Creates a new DelayQueue with no elements |
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*/ |
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public DelayQueue() {} |
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|
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/** |
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* Create a new DelayQueue with elements taken from the given |
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* collection of {@link Delayed} instances. |
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* |
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* @fixme Should the body be wrapped with try-lock-finally-unlock? |
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*/ |
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public DelayQueue(Collection<? extends E> c) { |
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this.addAll(c); |
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} |
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|
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public boolean offer(E x) { |
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lock.lock(); |
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try { |
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E first = q.peek(); |
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q.offer(x); |
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if (first == null || x.compareTo(first) < 0) |
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available.signalAll(); |
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return true; |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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public void put(E x) { |
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offer(x); |
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} |
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|
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public boolean offer(E x, long time, TimeUnit unit) { |
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return offer(x); |
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} |
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|
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public boolean add(E x) { |
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return offer(x); |
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} |
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|
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public E take() throws InterruptedException { |
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lock.lockInterruptibly(); |
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try { |
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for (;;) { |
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E first = q.peek(); |
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if (first == null) |
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available.await(); |
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else { |
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long delay = first.getDelay(TimeUnit.NANOSECONDS); |
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if (delay > 0) |
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available.awaitNanos(delay); |
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else { |
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E x = q.poll(); |
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assert x != null; |
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if (q.size() != 0) |
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available.signalAll(); // wake up other takers |
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return x; |
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|
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} |
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} |
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} |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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public E poll(long time, TimeUnit unit) throws InterruptedException { |
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lock.lockInterruptibly(); |
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long nanos = unit.toNanos(time); |
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try { |
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for (;;) { |
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E first = q.peek(); |
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if (first == null) { |
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if (nanos <= 0) |
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return null; |
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else |
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nanos = available.awaitNanos(nanos); |
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} |
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else { |
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long delay = first.getDelay(TimeUnit.NANOSECONDS); |
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if (delay > 0) { |
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if (delay > nanos) |
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delay = nanos; |
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long timeLeft = available.awaitNanos(delay); |
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nanos -= delay - timeLeft; |
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} |
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else { |
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E x = q.poll(); |
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assert x != null; |
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if (q.size() != 0) |
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available.signalAll(); |
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return x; |
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} |
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} |
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} |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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|
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public E poll() { |
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lock.lock(); |
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try { |
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E first = q.peek(); |
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if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0) |
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return null; |
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else { |
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E x = q.poll(); |
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assert x != null; |
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if (q.size() != 0) |
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available.signalAll(); |
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return x; |
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} |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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public E peek() { |
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lock.lock(); |
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try { |
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return q.peek(); |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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public int size() { |
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lock.lock(); |
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try { |
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return q.size(); |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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public void clear() { |
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lock.lock(); |
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try { |
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q.clear(); |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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public int remainingCapacity() { |
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return Integer.MAX_VALUE; |
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} |
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|
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public Object[] toArray() { |
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lock.lock(); |
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try { |
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return q.toArray(); |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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public <T> T[] toArray(T[] array) { |
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lock.lock(); |
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try { |
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return q.toArray(array); |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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public boolean remove(Object x) { |
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lock.lock(); |
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try { |
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return q.remove(x); |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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public Iterator<E> iterator() { |
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lock.lock(); |
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try { |
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return new Itr(q.iterator()); |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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private class Itr<E> implements Iterator<E> { |
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private final Iterator<E> iter; |
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Itr(Iterator<E> i) { |
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iter = i; |
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} |
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|
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public boolean hasNext() { |
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return iter.hasNext(); |
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} |
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|
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public E next() { |
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lock.lock(); |
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try { |
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return iter.next(); |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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|
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public void remove() { |
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lock.lock(); |
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try { |
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iter.remove(); |
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} |
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finally { |
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lock.unlock(); |
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} |
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} |
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} |
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|
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} |
