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package com.sun.enterprise.resource.pool.waitqueue;

import java.util.Collection;

/**
 * Represents the pool wait queue

 * To plug-in multiple implementation of wait-queue

 *
 * @author Jagadish Ramu
 */
public interface PoolWaitQueue {
    String DEFAULT_WAIT_QUEUE = "DEFAULT_WAIT_QUEUE";
    String THREAD_PRIORITY_BASED_WAIT_QUEUE = "THREAD_PRIORITY_BASED_WAIT_QUEUE";

    /**
     * returns the length of wait queue
     * @return length of wait queue.
     */
    int getQueueLength();

    /**
     * resource requesting thread will be added to queue

     * and the object on which it is made to wait is returned
     * @param o Object
     */
    void addToQueue(Object o);

    /**
     * removes the specified object (resource request) from the queue
     * @param o Object
     * @return boolean indicating whether the object was removed or not
     */
    boolean removeFromQueue(Object o);

    /**
     * removes the first object (resource request) from the queue
     */
    /*
    Object removeFirst();
    */

    /**
     * removes the first object (resource request) from the queue
     * @return Object first object
     */
    Object remove();

    /**
     * returns (does not remove) the first object (resource request) from the queue
     * @return Object first object
     */
    Object peek();

    /**
     * used to get access to the list of waiting clients

     * Useful in case of rolling over from one pool to another
     * eg: transparent-dynamic-pool-reconfiguration.
     * @return Collection
     */
    Collection getQueueContents();
}