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 * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
 * 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.
 *
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package com.sun.jdi.event;

import com.sun.jdi.Mirror;
import com.sun.jdi.VMDisconnectedException;
import com.sun.jdi.VirtualMachine;
import com.sun.jdi.request.EventRequest;

/**
 * Manager of incoming debugger events for a target VM.
 * Events are always grouped in {@link EventSet}s.
 * EventSets generated by the debugger back end can be read
 * here. There is one instance of EventQueue assigned to a particular
 * {@link VirtualMachine VirtualMachine}.
 * <P>
 * Some events cause the suspension of the target VM - event requests
 * ({@link com.sun.jdi.request}) with a
 * {@link EventRequest#suspendPolicy() suspend policy}
 * of {@link EventRequest#SUSPEND_ALL SUSPEND_ALL}
 * or {@link EventRequest#SUSPEND_EVENT_THREAD
 * SUSPEND_EVENT_THREAD} and sometimes {@link VMStartEvent}.
 * If these suspensions are not resumed the target VM will hang.
 * Thus, it is always good policy to
 * {@link #remove() remove()} every EventSet from the event queue until
 * an EventSet containing a {@link VMDisconnectEvent} is read.
 * Unless {@link VirtualMachine#resume() resume} is
 * being handled in another way, each EventSet should invoke
 * {@link EventSet#resume()}.
 *
 * @see EventSet
 * @see VirtualMachine
 *
 * @author Robert Field
 * @since  1.3
 */
public interface EventQueue extends Mirror {

    /**
     * Waits forever for the next available event.
     *
     * @return the next {@link EventSet}.
     * @throws InterruptedException if any thread has interrupted this thread.
     * @throws VMDisconnectedException if the connection
     * to the target VM is no longer available. Note this will always
     * be preceded by a {@link VMDisconnectEvent}.
     */
    EventSet remove() throws InterruptedException;

    /**
     * Waits a specified time for the next available event.
     *
     * @param timeout Time in milliseconds to wait for the next event
     * @return the next {@link EventSet}, or null if there is a timeout.
     * @throws InterruptedException if any thread has interrupted
     * this thread.
     * @throws VMDisconnectedException if the connection
     * to the target VM is no longer available. Note this will always
     * be preceded by a {@link VMDisconnectEvent}.
     * @throws IllegalArgumentException if the timeout argument
     * contains an illegal value.
     */
    EventSet remove(long timeout) throws InterruptedException;
}
