Example usage for java.util Deque offerFirst

Introduction

In this page you can find the example usage for java.util Deque offerFirst.

Prototype

boolean offerFirst(E e);

Source Link

Document

Inserts the specified element at the front of this deque unless it would violate capacity restrictions.

Usage

From source file:Main.java

public static void main(String[] args) {

    Deque<Integer> deque = new ArrayDeque<Integer>(8);

    deque.add(1);//from  w w  w  .jav  a  2  s .  c o m
    deque.add(2);
    deque.add(3);
    deque.add(4);

    deque.offerFirst(10);

    System.out.println(deque);
}

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From source file:no.sesat.search.http.filters.SiteLocatorFilter.java

private static void doChainFilter(final FilterChain chain, final HttpServletRequest request,
        final HttpServletResponse response) throws IOException, ServletException {

    final HttpSession session = request.getSession();

    // fetch the user's deque
    final Deque<ServletRequest> deque = getUsersDeque(session);

    // lock to execute
    final ReentrantLock lock = (ReentrantLock) session.getAttribute(USER_REQUEST_LOCK);

    // deque has a time limit. start counting.
    long timeLeft = WAIT_TIME;

    try {/*from   www .j  av  a 2  s  .c  om*/
        // attempt to join deque
        if (deque.offerFirst(request)) {
            timeLeft = tryLock(request, deque, lock, timeLeft);
        }

        if (lock.isHeldByCurrentThread()) {

            // waiting is over. and we can execute
            chain.doFilter(request, response);

        } else {
            // we failed to execute. return 409 response.
            if (response instanceof HttpServletResponse) {

                LOG.warn(" -- response 409 "
                        + (0 < timeLeft ? "(More then " + REQUEST_QUEUE_SIZE + " requests already in queue)"
                                : "(Timeout: Waited " + WAIT_TIME + " ms)"));

                response.sendError(HttpServletResponse.SC_CONFLICT);
            }
        }
    } finally {

        // take out of deque first
        deque.remove(request);

        // release the lock, waiting up the next request
        if (lock.isHeldByCurrentThread()) {
            lock.unlock();
        }
    }
}

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From source file:org.apache.giraph.comm.flow_control.CreditBasedFlowControl.java

/**
 * Try to send as much as cached requests to a given worker
 *
 * @param taskId id of the worker to send cached requests to
 *///from w w w  . java 2 s . c  o  m
private void trySendCachedRequests(int taskId) {
    Deque<WritableRequest> requestDeque = perWorkerUnsentRequestMap.get(taskId);
    AdjustableSemaphore openRequestPermit = perWorkerOpenRequestMap.get(taskId).getLeft();
    while (true) {
        WritableRequest request;
        synchronized (requestDeque) {
            request = requestDeque.pollFirst();
            if (request == null) {
                break;
            }
            // See whether the sender client has any unused credit
            if (!openRequestPermit.tryAcquire()) {
                requestDeque.offerFirst(request);
                break;
            }
        }
        unsentRequestPermit.release();
        // At this point, we have a request, and we reserved a credit for the
        // sender client. So, we send the request to the client and update
        // the state.
        nettyClient.doSend(taskId, request);
        if (aggregateUnsentRequests.decrementAndGet() == 0) {
            synchronized (aggregateUnsentRequests) {
                aggregateUnsentRequests.notifyAll();
            }
        }
    }
}

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