What is Java Timer? Java Timer is used to schedule tasks for future execution in a background thread. Tasks may be scheduled for one-time execution, or for repeated execution at regular intervals.
How are tasks executed by Timer object? Each timer object has a single background thread that is used to execute all of the timer's tasks, sequentially.
Can Timer execute more than one task at a time?
The default implementation of Timer will execute the task only in sequential order. For example, if you've scheduled two task at 7 PM and 8 PM respectively. And if the first task takes 5 hours to complete, then the second task will only be executed only after 12'o clock.
How to make Java Timer to execute tasks concurrently?
Solution 1:
Create multiple timers. Each timer will execute one task at time. If you want to run three tasks subsequently, you need to create three different timer objects.
Solution 2:
Run all the tasks in a separate Thread. In the example given above, Timer thread will create one worker thread to execute the fist task at 7 PM and second task at 8 PM respectively.
Sample Code (Solution 2):
public class JavaTimer {
public static void main(String[] args) {
Timer timer = new Timer();
timer.schedule(new Task1(), Calendar.getInstance().getTime());
timer.schedule(new Task2(), Calendar.getInstance().getTime());
timer.schedule(new Task3(), Calendar.getInstance().getTime());
}
}
class TaskBase extends TimerTask
{
public String getName()
{
return this.getClass().getName();
}
@Override
public void run() {
//Creates a new thread for each task.
new Thread() {
public void run() {
runInAnotherThread();
}
}.start();
}
public void runInAnotherThread() {
System.out.println(getName()+" Scheduled Time: "+new Date(this.scheduledExecutionTime()));
System.out.println(getName()+" Executed Time: "+new Date());
doTask();
}
public void doTask()
{
System.out.println("Will be implemented by sub classes");
}
}
class Task1 extends TaskBase
{
public void doTask()
{
System.out.println("DoTask of Task1");
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("End of DoTask of Task1");
}
}
class Task2 extends TaskBase
{
public void doTask()
{
System.out.println("DoTask of Task2");
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("End of DoTask of Task2");
}
}
class Task3 extends TaskBase
{
public void doTask()
{
System.out.println("DoTask of Task3");
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("End of DoTask of Task3");
}
}
