Create two numbers. Call the first one number_of_spaces. Call the second one number_of_stars.

Set number_of_spaces to zero. Set number_of_stars to five.

Now output number_of_spaces spaces, and number_of_stars stars.
Add one to number_of_spaces, subtract one from number_of_stars.
Repeat previous two instructions until you're done.

Welcome to programming. Programming is thinking. When you get it working, see if you can think of a better algorithm.

Consider you have a counter (c) that goes from 1 to 5.
The number of stars you what to print is s = 6-c.
In this way,
when c values 1 s values 5,
when c values 2 s values 4,
when c values 3 s values 3,
and so on.
That's all you need.

public class Main {
public static void main(String[] args) {
long timeCheck;
long periodOfTime;
ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(2);
long initialDelay = 0; // ...