content: /*
   * 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/publicdomain/zero/1.0/
   */
  
  package java.util.concurrent;
  
  import java.util.Collection;
  import java.util.concurrent.locks.AbstractQueuedSynchronizer;
  
  /**
   * 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> {@code
   * 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 java.util.concurrent.locks.Lock}
   * implementations), that the &quot;lock&quot; 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. These methods are generally more efficient and
   * effective than loops. However, they do not establish any preference
   * order. For example, if thread A invokes {@code s.acquire(3}) and
   * thread B invokes {@code s.acquire(2)}, and two permits become
   * available, then there is no guarantee that thread B will obtain
   * them unless its acquire came first and Semaphore {@code s} is in
   * fair mode.
   *
   * <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 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 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 current = getState();
                  int next = current + releases;
                  if (next < current) // overflow
                      throw new Error("Maximum permit count exceeded");
                  if (compareAndSetState(current, next))
                      return true;
              }
          }
  
          final void reducePermits(int reductions) {
              for (;;) {
                  int current = getState();
                  int next = current - reductions;
                  if (next > current) // underflow
                      throw new Error("Permit count underflow");
                  if (compareAndSetState(current, next))
                      return;
              }
          }
  
          final int drainPermits() {
              for (;;) {
                  int current = getState();
                  if (current == 0 || compareAndSetState(current, 0))
                      return current;
              }
          }
      }
  
      /**
       * NonFair version
       */
      static final 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
       */
      static final class FairSync extends Sync {
          private static final long serialVersionUID = 2014338818796000944L;
  
          FairSync(int permits) {
              super(permits);
          }
  
          protected int tryAcquireShared(int acquires) {
              for (;;) {
                  if (hasQueuedPredecessors())
                      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 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 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 &quot;barging&quot; 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, 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. This method has the same effect as the
       * loop {@code for (int i = 0; i < permits; ++i) acquire();} except
       * that it atomically acquires the permits all at once:
       *
       * <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 and 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. This method has the same effect as the
       * loop {@code for (int i = 0; i < permits; ++i) acquireUninterruptibly();}
       * except that it atomically acquires the permits all at once:
       *
       * <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 and 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
       * &quot;barging&quot; 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 and 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, 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 thread
       * 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
       * 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() + "]";
      }
  }
  