Make use of getFirst/getLast

[SimonVerhoeven]

Is your feature request related to a problem? Please describe.

Not a problem, but there are some occurrences such as .get(scheduleHours.size() - 1) which could be replaced with getLast().

Describe the solution you'd like

To make use of the new convenience methods.

Additional context

similiarly, get(0) will be replaced by getFirst()

[SimonVerhoeven]

To help out: this is to leverage the advantages of https://openjdk.org/jeps/431

[nefelhhh]

hi can I take on this?

[SquidXTV]

hi can I take on this?

Yes, I am going to assign you to this. <3