Java 中的 Java.util.TimerTask 类

原文:https://www . geesforgeks . org/Java-util-time rtask-class-Java/

TimerTask 是 java.util 包中定义的抽象类。TimerTask 类定义了一个任务，该任务可以被安排为只运行一次，也可以重复运行多次。为了定义 TimerTask 对象，需要实现这个类，并且需要重写 run 方法。当定时器对象调度 run 方法时，run 方法被隐式调用。

注意:TimerTask 类的一个实例用于定义需要定期运行的任务。

构造函数:

  • Timertask () : Create a new timer task.

申报:

public abstract class TimerTask
        extends Object
        implements Runnable

方法:

  1. 取消():Java . util . timertask . cancel()取消此计时器任务

    语法:

    java public boolean cancel() Returns: true if this task is scheduled for one-time execution and has not yet run, or this task is scheduled for repeated execution. Returns false if the task was scheduled for one-time execution and has already run, or if the task was never scheduled, or if the task was already cancelled.

  2. run():Java . util . timertask . run()此计时器任务要执行的操作

    语法:

    java public abstract void run() Description: The action to be performed by this timer task

  3. scheduledExecutionTime():Java。乌提尔。timertask。预定执行

方法继承自 java.lang.Object 类

  • clone
  • be equal to
  • verdict
  • getClass(获取类)
  • hashCode(哈希代码)
  • notifyAll(通知所有人)
  • tostring
  • wait for

演示 TimerTask 类用法的 Java 程序

// Java program to demonstrate 
// working of TimerTask class
import java.util.Timer;
import java.util.TimerTask;

class Helper extends TimerTask
{
    public static int i = 0;
    public void run()
    {
        System.out.println("Timer ran" + ++i);
        if(i == 4)
        {
            synchronized(Test.obj)
            {
                Test.obj.notify();
            }
        }
    }

}

public class Test
{
    public static Test obj;
    public static void main(String[] args) throws InterruptedException
    {
        obj = new Test();

        // creating an instance of timer class
        Timer timer = new Timer();

        // creating an instance of task to be scheduled
        TimerTask task = new Helper();

        // scheduling the timer instance
        timer.schedule(task, 1000, 3000);

        // fetching the scheduled execution time of 
        // the most recent actual execution of the task
        System.out.println(task.scheduledExecutionTime());

        synchronized(obj)
        {
            //this thread waits until i reaches 4
            obj.wait();
        }

        //canceling the task assigned 
        System.out.println("Cancel the timer task: " + task.cancel());

        // at this point timer is still running 
        // without any task assigned to it

        // canceling the timer instance created
        timer.cancel();
    }
}

输出:

1495715853591
Timer ran 1
Timer ran 2
Timer ran 3
Timer ran 4
Cancel the timer task: true

参考资料:

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