schedulertask.java

来自「数据库远程同步软件NetBeans项目源文件 项目采用Jdesktop集成组件」· Java 代码 · 共 63 行

package databasesyncdesktopapplication.PlanTaskPool;

import java.util.TimerTask;


/**
 * A task that can be scheduled for recurring execution by a {@link Scheduler}.
 */
public abstract class SchedulerTask implements Runnable {

    final Object lock = new Object();

    int state = VIRGIN;
    static final int VIRGIN = 0;
    static final int SCHEDULED = 1;
    static final int CANCELLED = 2;

    TimerTask timerTask;

/**
 * Creates a new scheduler task.
 */

    protected SchedulerTask() {
    }

/**
 * The action to be performed by this scheduler task.
 */

    public abstract void run();

/**
 * Cancels this scheduler task.
 * <p>
 * This method may be called repeatedly; the second and subsequent calls have no effect.
 * @return true if this task was already scheduled to run
 */

    public boolean cancel() {
        synchronized(lock) {
            if (timerTask != null) {
                timerTask.cancel();
            }
            boolean result = (state == SCHEDULED);
            state = CANCELLED;
            return result;
        }
    }

/**
 * Returns the <i>scheduled</i> execution time of the most recent actual execution of this task. (If this method is invoked while task execution is in progress, the return value is the scheduled execution time of the ongoing task execution.)
 * @return the time at which the most recent execution of this task was scheduled to occur, in the format returned by <code>Date.getTime()</code>. The return value is undefined if the task has yet to commence its first execution.
 */

    public long scheduledExecutionTime() {
        synchronized(lock) {
            return timerTask == null ? 0 : timerTask.scheduledExecutionTime();
        }
    }

}