Examples of java.util.concurrent.Semaphore.tryAcquire()

java.util.concurrent.Semaphore.tryAcquire()
Acquires a permit from this semaphore, only if one is available at the time of invocation.
Acquires a permit, if one is available and returns immediately, with the value {@code true}, reducing the number of available permits by one.
If no permit is available then this method will return immediately with the value {@code false}.
Even when this semaphore has been set to use a fair ordering policy, a call to {@code tryAcquire()} willimmediately 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

        creationSemaphore = new Semaphore(1, true);
        socketCreationMap.put(key, creationSemaphore);
      }
    }
    try {
      boolean retval = creationSemaphore.tryAcquire(10, TimeUnit.SECONDS);
      if (!retval) {
        throw new IOException("Could not acquire IO Semaphore'" + key
            + "' after 10 seconds -- giving up ");
      }
    } catch (InterruptedException e) {

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                Thread.sleep(500);
            }
        }


        // Wait until all updates return
        sem.tryAcquire(15, TimeUnit.SECONDS);
        
        // Verify that server is following and has the same epoch as the leader
        Assert.assertTrue("Not following", qu.getPeer(index).peer.follower != null);
        long epochF = (qu.getPeer(index).peer.getActiveServer().getZxid() >> 32L);
        long epochL = (leader.getEpoch() >> 32L);

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                return null;
            }
        });


        // Wait for the thread to start
        assertTrue(signal.tryAcquire(5, TimeUnit.SECONDS));


        // Attempt to ensure that test thread is blocked waiting for an object
        Thread.sleep(500);


        pool.invalidateObject(Integer.valueOf(1), object2);

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        Thread.sleep(500);


        pool.invalidateObject(Integer.valueOf(1), object2);


        assertTrue("Call to invalidateObject did not unblock pool waiters.",
                   signal.tryAcquire(2, TimeUnit.SECONDS));


        if (result.get() != null) {
            throw new AssertionError(result.get());
        }
    }

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        Semaphore lock = e.getRole() == Role.Consumer ? e.getConsumerLock(true)
                : e.getProviderLock(true);
        try {
            dispatch(e);
            if (timeout > 0) {
                if (!lock.tryAcquire(timeout, TimeUnit.MILLISECONDS)) {
                    throw new TimeoutException();
                }
            } else {
                lock.acquire();
            }

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          try { 
            s.acquire();
          } catch (InterruptedException ix) {}
        } else { 
          try { 
            s.tryAcquire(graceperiod, TimeUnit.MILLISECONDS);
          } catch (InterruptedException ix) {}
        }
      }
      result = bpcRef.get();
      st.close();

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  public boolean tryAcquirePermitOnCascClientSemaphore(CascadedClient cascClient, int oti, ISCMPMessageCallback callback) {
    boolean permit = false;
    Semaphore cascClientSemaphore = cascClient.getCascClientSemaphore();
    try {
      LOGGER.trace("acquire permit callback=" + callback.getClass());
      permit = cascClientSemaphore.tryAcquire(oti, TimeUnit.MILLISECONDS);
    } catch (InterruptedException ex) {
      // thread interrupted during acquire a permit on semaphore
      callback.receive(ex);
      LOGGER.warn("thread interrupted during acquire a permit on semaphore service=" + cascClient.getServiceName() + " "
          + ex.toString());

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                          stackLogger.logDebug("trying to acquiring semaphore for message " + message);
                        }
                        // we try to acquire here so that if the result if false because it is already acquired
                        // we acquire it in the thread to avoid blocking other messages with a different call id
                        // that could be processed in parallel
                        final boolean acquired = callIdSemaphore.tryAcquire(0, TimeUnit.SECONDS);                                                
                        
                        Thread messageDispatchTask = new Thread() {
                          @Override
                          public void run() {
                            // if it was not acquired above

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  public boolean tryAcquirePermitOnCascClientSemaphore(CascadedClient cascClient, int oti, ISCMPMessageCallback callback) {
    boolean permit = false;
    Semaphore cascClientSemaphore = cascClient.getCascClientSemaphore();
    try {
      LOGGER.trace("acquire permit callback=" + callback.getClass());
      permit = cascClientSemaphore.tryAcquire(oti, TimeUnit.MILLISECONDS);
    } catch (InterruptedException ex) {
      // thread interrupted during acquire a permit on semaphore
      callback.receive(ex);
      LOGGER.warn("thread interrupted during acquire a permit on semaphore service=" + cascClient.getServiceName() + " "
          + ex.toString());

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            try {
                for (int i = 0; i < configs.length; i++) {
                    configs[i].delete();
                }
                if (!sem.tryAcquire(1, TimeUnit.SECONDS)) {
                    throw new IOException("Not all instances were removed in time.");
                }
            }
            finally {
                tracker.close();

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