/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain. Use, modify, and
 * redistribute this code in any way without acknowledgement.
 */

package java.util.concurrent;

/**
 * Something (usually a task) that can be cancelled.  Cancellation is
 * performed by the <tt>cancel</tt> method.  Additional methods are
 * provided to determine if the task completed normally or was
 * cancelled.
 *
 * @since 1.5
 *
 * @spec JSR-166
 * @revised $Date: 2003/06/06 18:42:17 $
 * @editor $Author: dl $
 */
public interface Cancellable {

    /**
     * Cancels execution of this task if it has not already completed.
     * If this task has not started when <tt>cancel</tt> is called, this
     * task will never run.  If the task has already started, then
     * the <tt>interruptIfRunning</tt> parameter determines whether the
     * thread executing this task should be interrupted in an attempt to
     * stop the task.
     *
     * @param interruptIfRunning <tt>true</tt> if the thread executing this
     * task should be interrupted; otherwise, in-progress tasks are allowed
     * to complete
     * @return <tt>true</tt> if task has not already completed or been
     * cancelled; <tt>false</tt> otherwise
     */
    boolean cancel(boolean mayInterruptIfRunning);

    /**
     * Returns <tt>true</tt> if this task was cancelled before it completed
     * normally.
     *
     * @return <tt>true</tt> if task was cancelled before it completed
     */
    boolean isCancelled();

    /**
     * Returns <tt>true</tt> if this task ran to completion or was cancelled.
     *
     * @return <tt>true</tt> if task completed normally or was cancelled
     */
    boolean isDone();
}