--- /dev/null
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package edu.tamu.aser.internaljuc;
+import java.util.*;
+
+import edu.tamu.aser.internaljuc.Reex_TimeUnit;
+
+
+/**
+ * A counting semaphore. Conceptually, a semaphore maintains a set of
+ * permits. Each {@link #acquire} blocks if necessary until a permit is
+ * available, and then takes it. Each {@link #release} adds a permit,
+ * potentially releasing a blocking acquirer.
+ * However, no actual permit objects are used; the {@code Semaphore} just
+ * keeps a count of the number available and acts accordingly.
+ *
+ * <p>Semaphores are often used to restrict the number of threads than can
+ * access some (physical or logical) resource. For example, here is
+ * a class that uses a semaphore to control access to a pool of items:
+ * <pre>
+ * class Pool {
+ * private static final int MAX_AVAILABLE = 100;
+ * private final Semaphore available = new Semaphore(MAX_AVAILABLE, true);
+ *
+ * public Object getItem() throws InterruptedException {
+ * available.acquire();
+ * return getNextAvailableItem();
+ * }
+ *
+ * public void putItem(Object x) {
+ * if (markAsUnused(x))
+ * available.release();
+ * }
+ *
+ * // Not a particularly efficient data structure; just for demo
+ *
+ * protected Object[] items = ... whatever kinds of items being managed
+ * protected boolean[] used = new boolean[MAX_AVAILABLE];
+ *
+ * protected synchronized Object getNextAvailableItem() {
+ * for (int i = 0; i < MAX_AVAILABLE; ++i) {
+ * if (!used[i]) {
+ * used[i] = true;
+ * return items[i];
+ * }
+ * }
+ * return null; // not reached
+ * }
+ *
+ * protected synchronized boolean markAsUnused(Object item) {
+ * for (int i = 0; i < MAX_AVAILABLE; ++i) {
+ * if (item == items[i]) {
+ * if (used[i]) {
+ * used[i] = false;
+ * return true;
+ * } else
+ * return false;
+ * }
+ * }
+ * return false;
+ * }
+ *
+ * }
+ * </pre>
+ *
+ * <p>Before obtaining an item each thread must acquire a permit from
+ * the semaphore, guaranteeing that an item is available for use. When
+ * the thread has finished with the item it is returned back to the
+ * pool and a permit is returned to the semaphore, allowing another
+ * thread to acquire that item. Note that no synchronization lock is
+ * held when {@link #acquire} is called as that would prevent an item
+ * from being returned to the pool. The semaphore encapsulates the
+ * synchronization needed to restrict access to the pool, separately
+ * from any synchronization needed to maintain the consistency of the
+ * pool itself.
+ *
+ * <p>A semaphore initialized to one, and which is used such that it
+ * only has at most one permit available, can serve as a mutual
+ * exclusion lock. This is more commonly known as a <em>binary
+ * semaphore</em>, because it only has two states: one permit
+ * available, or zero permits available. When used in this way, the
+ * binary semaphore has the property (unlike many {@link Reex_Lock}
+ * implementations), that the "lock" can be released by a
+ * thread other than the owner (as semaphores have no notion of
+ * ownership). This can be useful in some specialized contexts, such
+ * as deadlock recovery.
+ *
+ * <p> The constructor for this class optionally accepts a
+ * <em>fairness</em> parameter. When set false, this class makes no
+ * guarantees about the order in which threads acquire permits. In
+ * particular, <em>barging</em> is permitted, that is, a thread
+ * invoking {@link #acquire} can be allocated a permit ahead of a
+ * thread that has been waiting - logically the new thread places itself at
+ * the head of the queue of waiting threads. When fairness is set true, the
+ * semaphore guarantees that threads invoking any of the {@link
+ * #acquire() acquire} methods are selected to obtain permits in the order in
+ * which their invocation of those methods was processed
+ * (first-in-first-out; FIFO). Note that FIFO ordering necessarily
+ * applies to specific internal points of execution within these
+ * methods. So, it is possible for one thread to invoke
+ * {@code acquire} before another, but reach the ordering point after
+ * the other, and similarly upon return from the method.
+ * Also note that the untimed {@link #tryAcquire() tryAcquire} methods do not
+ * honor the fairness setting, but will take any permits that are
+ * available.
+ *
+ * <p>Generally, semaphores used to control resource access should be
+ * initialized as fair, to ensure that no thread is starved out from
+ * accessing a resource. When using semaphores for other kinds of
+ * synchronization control, the throughput advantages of non-fair
+ * ordering often outweigh fairness considerations.
+ *
+ * <p>This class also provides convenience methods to {@link
+ * #acquire(int) acquire} and {@link #release(int) release} multiple
+ * permits at a time. Beware of the increased risk of indefinite
+ * postponement when these methods are used without fairness set true.
+ *
+ * <p>Memory consistency effects: Actions in a thread prior to calling
+ * a "release" method such as {@code release()}
+ * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
+ * actions following a successful "acquire" method such as {@code acquire()}
+ * in another thread.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ *
+ */
+
+public class Reex_Semaphore implements java.io.Serializable {
+ private static final long serialVersionUID = -3222578661600680210L;
+ /** All mechanics via AbstractQueuedSynchronizer subclass */
+ private final Sync sync;
+
+ /**
+ * Synchronization implementation for semaphore. Uses AQS state
+ * to represent permits. Subclassed into fair and nonfair
+ * versions.
+ */
+ abstract static class Sync extends Reex_AbstractQueuedSynchronizer {
+ private static final long serialVersionUID = 1192457210091910933L;
+
+ Sync(int permits) {
+ setState(permits);
+ }
+
+ final int getPermits() {
+ return getState();
+ }
+
+ final int nonfairTryAcquireShared(int acquires) {
+ for (;;) {
+ int available = getState();
+ int remaining = available - acquires;
+ if (remaining < 0 ||
+ compareAndSetState(available, remaining))
+ return remaining;
+ }
+ }
+
+ protected final boolean tryReleaseShared(int releases) {
+ for (;;) {
+ int p = getState();
+ if (compareAndSetState(p, p + releases))
+ return true;
+ }
+ }
+
+ final void reducePermits(int reductions) {
+ for (;;) {
+ int current = getState();
+ int next = current - reductions;
+ if (compareAndSetState(current, next))
+ return;
+ }
+ }
+
+ final int drainPermits() {
+ for (;;) {
+ int current = getState();
+ if (current == 0 || compareAndSetState(current, 0))
+ return current;
+ }
+ }
+ }
+
+ /**
+ * NonFair version
+ */
+ final static class NonfairSync extends Sync {
+ private static final long serialVersionUID = -2694183684443567898L;
+
+ NonfairSync(int permits) {
+ super(permits);
+ }
+
+ protected int tryAcquireShared(int acquires) {
+ return nonfairTryAcquireShared(acquires);
+ }
+ }
+
+ /**
+ * Fair version
+ */
+ final static class FairSync extends Sync {
+ private static final long serialVersionUID = 2014338818796000944L;
+
+ FairSync(int permits) {
+ super(permits);
+ }
+
+ protected int tryAcquireShared(int acquires) {
+ for (;;) {
+ if (getFirstQueuedThread() != Thread.currentThread() &&
+ hasQueuedThreads())
+ return -1;
+ int available = getState();
+ int remaining = available - acquires;
+ if (remaining < 0 ||
+ compareAndSetState(available, remaining))
+ return remaining;
+ }
+ }
+ }
+
+ /**
+ * Creates a {@code Semaphore} with the given number of
+ * permits and nonfair fairness setting.
+ *
+ * @param permits the initial number of permits available.
+ * This value may be negative, in which case releases
+ * must occur before any acquires will be granted.
+ */
+ public Reex_Semaphore(int permits) {
+ sync = new NonfairSync(permits);
+ }
+
+ /**
+ * Creates a {@code Semaphore} with the given number of
+ * permits and the given fairness setting.
+ *
+ * @param permits the initial number of permits available.
+ * This value may be negative, in which case releases
+ * must occur before any acquires will be granted.
+ * @param fair {@code true} if this semaphore will guarantee
+ * first-in first-out granting of permits under contention,
+ * else {@code false}
+ */
+ public Reex_Semaphore(int permits, boolean fair) {
+ sync = (fair)? new FairSync(permits) : new NonfairSync(permits);
+ }
+
+ /**
+ * Acquires a permit from this semaphore, blocking until one is
+ * available, or the thread is {@linkplain Thread#interrupt interrupted}.
+ *
+ * <p>Acquires a permit, if one is available and returns immediately,
+ * reducing the number of available permits by one.
+ *
+ * <p>If no permit is available then the current thread becomes
+ * disabled for thread scheduling purposes and lies dormant until
+ * one of two things happens:
+ * <ul>
+ * <li>Some other thread invokes the {@link #release} method for this
+ * semaphore and the current thread is next to be assigned a permit; or
+ * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+ * the current thread.
+ * </ul>
+ *
+ * <p>If the current thread:
+ * <ul>
+ * <li>has its interrupted status set on entry to this method; or
+ * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+ * for a permit,
+ * </ul>
+ * then {@link InterruptedException} is thrown and the current thread's
+ * interrupted status is cleared.
+ *
+ * @throws InterruptedException if the current thread is interrupted
+ */
+ public void acquire() throws InterruptedException {
+ sync.acquireSharedInterruptibly(1);
+ }
+
+ /**
+ * Acquires a permit from this semaphore, blocking until one is
+ * available.
+ *
+ * <p>Acquires a permit, if one is available and returns immediately,
+ * reducing the number of available permits by one.
+ *
+ * <p>If no permit is available then the current thread becomes
+ * disabled for thread scheduling purposes and lies dormant until
+ * some other thread invokes the {@link #release} method for this
+ * semaphore and the current thread is next to be assigned a permit.
+ *
+ * <p>If the current thread is {@linkplain Thread#interrupt interrupted}
+ * while waiting for a permit then it will continue to wait, but the
+ * time at which the thread is assigned a permit may change compared to
+ * the time it would have received the permit had no interruption
+ * occurred. When the thread does return from this method its interrupt
+ * status will be set.
+ */
+ public void acquireUninterruptibly() {
+ sync.acquireShared(1);
+ }
+
+ /**
+ * Acquires a permit from this semaphore, only if one is available at the
+ * time of invocation.
+ *
+ * <p>Acquires a permit, if one is available and returns immediately,
+ * with the value {@code true},
+ * reducing the number of available permits by one.
+ *
+ * <p>If no permit is available then this method will return
+ * immediately with the value {@code false}.
+ *
+ * <p>Even when this semaphore has been set to use a
+ * fair ordering policy, a call to {@code tryAcquire()} <em>will</em>
+ * immediately acquire a permit if one is available, whether or not
+ * other threads are currently waiting.
+ * This "barging" behavior can be useful in certain
+ * circumstances, even though it breaks fairness. If you want to honor
+ * the fairness setting, then use
+ * {@link #tryAcquire(long, TimeUnit) tryAcquire(0, TimeUnit.SECONDS) }
+ * which is almost equivalent (it also detects interruption).
+ *
+ * @return {@code true} if a permit was acquired and {@code false}
+ * otherwise
+ */
+ public boolean tryAcquire() {
+ return sync.nonfairTryAcquireShared(1) >= 0;
+ }
+
+ /**
+ * Acquires a permit from this semaphore, if one becomes available
+ * within the given waiting time and the current thread has not
+ * been {@linkplain Thread#interrupt interrupted}.
+ *
+ * <p>Acquires a permit, if one is available and returns immediately,
+ * with the value {@code true},
+ * reducing the number of available permits by one.
+ *
+ * <p>If no permit is available then the current thread becomes
+ * disabled for thread scheduling purposes and lies dormant until
+ * one of three things happens:
+ * <ul>
+ * <li>Some other thread invokes the {@link #release} method for this
+ * semaphore and the current thread is next to be assigned a permit; or
+ * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+ * the current thread; or
+ * <li>The specified waiting time elapses.
+ * </ul>
+ *
+ * <p>If a permit is acquired then the value {@code true} is returned.
+ *
+ * <p>If the current thread:
+ * <ul>
+ * <li>has its interrupted status set on entry to this method; or
+ * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+ * to acquire a permit,
+ * </ul>
+ * then {@link InterruptedException} is thrown and the current thread's
+ * interrupted status is cleared.
+ *
+ * <p>If the specified waiting time elapses then the value {@code false}
+ * is returned. If the time is less than or equal to zero, the method
+ * will not wait at all.
+ *
+ * @param timeout the maximum time to wait for a permit
+ * @param unit the time unit of the {@code timeout} argument
+ * @return {@code true} if a permit was acquired and {@code false}
+ * if the waiting time elapsed before a permit was acquired
+ * @throws InterruptedException if the current thread is interrupted
+ */
+ public boolean tryAcquire(long timeout, Reex_TimeUnit unit)
+ throws InterruptedException {
+ return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));
+ }
+
+ /**
+ * Releases a permit, returning it to the semaphore.
+ *
+ * <p>Releases a permit, increasing the number of available permits by
+ * one. If any threads are trying to acquire a permit, then one is
+ * selected and given the permit that was just released. That thread
+ * is (re)enabled for thread scheduling purposes.
+ *
+ * <p>There is no requirement that a thread that releases a permit must
+ * have acquired that permit by calling {@link #acquire}.
+ * Correct usage of a semaphore is established by programming convention
+ * in the application.
+ */
+ public void release() {
+ sync.releaseShared(1);
+ }
+
+ /**
+ * Acquires the given number of permits from this semaphore,
+ * blocking until all are available,
+ * or the thread is {@linkplain Thread#interrupt interrupted}.
+ *
+ * <p>Acquires the given number of permits, if they are available,
+ * and returns immediately, reducing the number of available permits
+ * by the given amount.
+ *
+ * <p>If insufficient permits are available then the current thread becomes
+ * disabled for thread scheduling purposes and lies dormant until
+ * one of two things happens:
+ * <ul>
+ * <li>Some other thread invokes one of the {@link #release() release}
+ * methods for this semaphore, the current thread is next to be assigned
+ * permits and the number of available permits satisfies this request; or
+ * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+ * the current thread.
+ * </ul>
+ *
+ * <p>If the current thread:
+ * <ul>
+ * <li>has its interrupted status set on entry to this method; or
+ * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+ * for a permit,
+ * </ul>
+ * then {@link InterruptedException} is thrown and the current thread's
+ * interrupted status is cleared.
+ * Any permits that were to be assigned to this thread are instead
+ * assigned to other threads trying to acquire permits, as if
+ * permits had been made available by a call to {@link #release()}.
+ *
+ * @param permits the number of permits to acquire
+ * @throws InterruptedException if the current thread is interrupted
+ * @throws IllegalArgumentException if {@code permits} is negative
+ */
+ public void acquire(int permits) throws InterruptedException {
+ if (permits < 0) throw new IllegalArgumentException();
+ sync.acquireSharedInterruptibly(permits);
+ }
+
+ /**
+ * Acquires the given number of permits from this semaphore,
+ * blocking until all are available.
+ *
+ * <p>Acquires the given number of permits, if they are available,
+ * and returns immediately, reducing the number of available permits
+ * by the given amount.
+ *
+ * <p>If insufficient permits are available then the current thread becomes
+ * disabled for thread scheduling purposes and lies dormant until
+ * some other thread invokes one of the {@link #release() release}
+ * methods for this semaphore, the current thread is next to be assigned
+ * permits and the number of available permits satisfies this request.
+ *
+ * <p>If the current thread is {@linkplain Thread#interrupt interrupted}
+ * while waiting for permits then it will continue to wait and its
+ * position in the queue is not affected. When the thread does return
+ * from this method its interrupt status will be set.
+ *
+ * @param permits the number of permits to acquire
+ * @throws IllegalArgumentException if {@code permits} is negative
+ *
+ */
+ public void acquireUninterruptibly(int permits) {
+ if (permits < 0) throw new IllegalArgumentException();
+ sync.acquireShared(permits);
+ }
+
+ /**
+ * Acquires the given number of permits from this semaphore, only
+ * if all are available at the time of invocation.
+ *
+ * <p>Acquires the given number of permits, if they are available, and
+ * returns immediately, with the value {@code true},
+ * reducing the number of available permits by the given amount.
+ *
+ * <p>If insufficient permits are available then this method will return
+ * immediately with the value {@code false} and the number of available
+ * permits is unchanged.
+ *
+ * <p>Even when this semaphore has been set to use a fair ordering
+ * policy, a call to {@code tryAcquire} <em>will</em>
+ * immediately acquire a permit if one is available, whether or
+ * not other threads are currently waiting. This
+ * "barging" behavior can be useful in certain
+ * circumstances, even though it breaks fairness. If you want to
+ * honor the fairness setting, then use {@link #tryAcquire(int,
+ * long, TimeUnit) tryAcquire(permits, 0, TimeUnit.SECONDS) }
+ * which is almost equivalent (it also detects interruption).
+ *
+ * @param permits the number of permits to acquire
+ * @return {@code true} if the permits were acquired and
+ * {@code false} otherwise
+ * @throws IllegalArgumentException if {@code permits} is negative
+ */
+ public boolean tryAcquire(int permits) {
+ if (permits < 0) throw new IllegalArgumentException();
+ return sync.nonfairTryAcquireShared(permits) >= 0;
+ }
+
+ /**
+ * Acquires the given number of permits from this semaphore, if all
+ * become available within the given waiting time and the current
+ * thread has not been {@linkplain Thread#interrupt interrupted}.
+ *
+ * <p>Acquires the given number of permits, if they are available and
+ * returns immediately, with the value {@code true},
+ * reducing the number of available permits by the given amount.
+ *
+ * <p>If insufficient permits are available then
+ * the current thread becomes disabled for thread scheduling
+ * purposes and lies dormant until one of three things happens:
+ * <ul>
+ * <li>Some other thread invokes one of the {@link #release() release}
+ * methods for this semaphore, the current thread is next to be assigned
+ * permits and the number of available permits satisfies this request; or
+ * <li>Some other thread {@linkplain Thread#interrupt interrupts}
+ * the current thread; or
+ * <li>The specified waiting time elapses.
+ * </ul>
+ *
+ * <p>If the permits are acquired then the value {@code true} is returned.
+ *
+ * <p>If the current thread:
+ * <ul>
+ * <li>has its interrupted status set on entry to this method; or
+ * <li>is {@linkplain Thread#interrupt interrupted} while waiting
+ * to acquire the permits,
+ * </ul>
+ * then {@link InterruptedException} is thrown and the current thread's
+ * interrupted status is cleared.
+ * Any permits that were to be assigned to this thread, are instead
+ * assigned to other threads trying to acquire permits, as if
+ * the permits had been made available by a call to {@link #release()}.
+ *
+ * <p>If the specified waiting time elapses then the value {@code false}
+ * is returned. If the time is less than or equal to zero, the method
+ * will not wait at all. Any permits that were to be assigned to this
+ * thread, are instead assigned to other threads trying to acquire
+ * permits, as if the permits had been made available by a call to
+ * {@link #release()}.
+ *
+ * @param permits the number of permits to acquire
+ * @param timeout the maximum time to wait for the permits
+ * @param unit the time unit of the {@code timeout} argument
+ * @return {@code true} if all permits were acquired and {@code false}
+ * if the waiting time elapsed before all permits were acquired
+ * @throws InterruptedException if the current thread is interrupted
+ * @throws IllegalArgumentException if {@code permits} is negative
+ */
+ public boolean tryAcquire(int permits, long timeout, Reex_TimeUnit unit)
+ throws InterruptedException {
+ if (permits < 0) throw new IllegalArgumentException();
+ return sync.tryAcquireSharedNanos(permits, unit.toNanos(timeout));
+ }
+
+ /**
+ * Releases the given number of permits, returning them to the semaphore.
+ *
+ * <p>Releases the given number of permits, increasing the number of
+ * available permits by that amount.
+ * If any threads are trying to acquire permits, then one
+ * is selected and given the permits that were just released.
+ * If the number of available permits satisfies that thread's request
+ * then that thread is (re)enabled for thread scheduling purposes;
+ * otherwise the thread will wait until sufficient permits are available.
+ * If there are still permits available
+ * after this thread's request has been satisfied, then those permits
+ * are assigned in turn to other threads trying to acquire permits.
+ *
+ * <p>There is no requirement that a thread that releases a permit must
+ * have acquired that permit by calling {@link Semaphore#acquire acquire}.
+ * Correct usage of a semaphore is established by programming convention
+ * in the application.
+ *
+ * @param permits the number of permits to release
+ * @throws IllegalArgumentException if {@code permits} is negative
+ */
+ public void release(int permits) {
+ if (permits < 0) throw new IllegalArgumentException();
+ sync.releaseShared(permits);
+ }
+
+ /**
+ * Returns the current number of permits available in this semaphore.
+ *
+ * <p>This method is typically used for debugging and testing purposes.
+ *
+ * @return the number of permits available in this semaphore
+ */
+ public int availablePermits() {
+ return sync.getPermits();
+ }
+
+ /**
+ * Acquires and returns all permits that are immediately available.
+ *
+ * @return the number of permits acquired
+ */
+ public int drainPermits() {
+ return sync.drainPermits();
+ }
+
+ /**
+ * Shrinks the number of available permits by the indicated
+ * reduction. This method can be useful in subclasses that use
+ * semaphores to track resources that become unavailable. This
+ * method differs from {@code acquire} in that it does not block
+ * waiting for permits to become available.
+ *
+ * @param reduction the number of permits to remove
+ * @throws IllegalArgumentException if {@code reduction} is negative
+ */
+ protected void reducePermits(int reduction) {
+ if (reduction < 0) throw new IllegalArgumentException();
+ sync.reducePermits(reduction);
+ }
+
+ /**
+ * Returns {@code true} if this semaphore has fairness set true.
+ *
+ * @return {@code true} if this semaphore has fairness set true
+ */
+ public boolean isFair() {
+ return sync instanceof FairSync;
+ }
+
+ /**
+ * Queries whether any threads are waiting to acquire. Note that
+ * because cancellations may occur at any time, a {@code true}
+ * return does not guarantee that any other thread will ever
+ * acquire. This method is designed primarily for use in
+ * monitoring of the system state.
+ *
+ * @return {@code true} if there may be other threads waiting to
+ * acquire the lock
+ */
+ public final boolean hasQueuedThreads() {
+ return sync.hasQueuedThreads();
+ }
+
+ /**
+ * Returns an estimate of the number of threads waiting to acquire.
+ * The value is only an estimate because the number of threads may
+ * change dynamically while this method traverses internal data
+ * structures. This method is designed for use in monitoring of the
+ * system state, not for synchronization control.
+ *
+ * @return the estimated number of threads waiting for this lock
+ */
+ public final int getQueueLength() {
+ return sync.getQueueLength();
+ }
+
+ /**
+ * Returns a collection containing threads that may be waiting to acquire.
+ * Because the actual set of threads may change dynamically while
+ * constructing this result, the returned collection is only a best-effort
+ * estimate. The elements of the returned collection are in no particular
+ * order. This method is designed to facilitate construction of
+ * subclasses that provide more extensive monitoring facilities.
+ *
+ * @return the collection of threads
+ */
+ protected Collection<Thread> getQueuedThreads() {
+ return sync.getQueuedThreads();
+ }
+
+ /**
+ * Returns a string identifying this semaphore, as well as its state.
+ * The state, in brackets, includes the String {@code "Permits ="}
+ * followed by the number of permits.
+ *
+ * @return a string identifying this semaphore, as well as its state
+ */
+ public String toString() {
+ return super.toString() + "[Permits = " + sync.getPermits() + "]";
+ }
+}
projects / Benchmarks_CSolver.git / blobdiff