Keeping track of currentTimeMillis

Question

I need to create an object that will stop execution for a certain amount of time using its own class methods. How do I have a program keep track of passing time and execute a function when a specified amount of time has passed.

I imagine .......

long pause; //a variable storing pause length in milliseconds.............
long currentTime; // which store the time of execution of the pause ,............. 

and when another variable tracking time has the same value as currentTime + pause, the next line of code is executed. Is it possible to make a variable that for a short period changes every millisecond as time passes?

Answer 1

For a simple solution, you could just use Thread#sleep

public void waitForExecution(long pause) throws InterruptedException { 
    // Perform some actions...
    Thread.sleep(pause);
    // Perform next set of actions
}

With a timer...

public class TimerTest {

    public static void main(String[] args) {
        Timer timer = new Timer("Happy", false);
        timer.schedule(new TimerTask() {

            @Override
            public void run() {
                System.out.println("Hello, I'm from the future!");
            }
        }, 5000);

        System.out.println("Hello, I'm from the present");
    }
}

And with a loop

long startAt = System.currentTimeMillis();
long pause = 5000;
System.out.println(DateFormat.getTimeInstance().format(new Date()));
while ((startAt + pause) > System.currentTimeMillis()) {
    // Waiting...
}
System.out.println(DateFormat.getTimeInstance().format(new Date()));

Note, this is more expensive then the other two solutions as the loop continues to consume CPU cycles, where as the Thread#sleep and Timer use a internal scheduling mechanism that allows the threads to idle (and not consume cycles)