JAVA中的定时调度(Timer和TimerTask)

import java.util.TimerTask;
import java.util.Date;
import java.util.Timer;
import java.text.SimpleDateFormat;

class ShowDateTask extends TimerTask
{
public void run()
{
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-DD HH:mm:ss:SSS");
System.out.println("当前时间是:" + sdf.format(new Date()));
}
}

class Hello
{
public static void main(String[] args)
{
ShowDateTask sdt = new ShowDateTask();
Timer t = new Timer();
t.schedule(sdt,3000,5000);
}

public static void sleep(int timeSpan)
{
try
{
Thread.sleep(timeSpan);
}
catch (Exception e)
{
System.out.println(e);
}
}
}