Hi jade, and welcome to the Ranch.
First of all you need to understand some rules of posting on this site.
Don't worry they are just like the general rules to post on any forum around the web. So, it is my request to read them carefully.
HowToAnswerOnJavaRanch and HowToAskQuestionsOnJavaRanch
Beware of saying multidimensional array, because Java doesn’t have them. It has arrays of arrays instead, which are better.
You should be doing largest and smallest on a 1‑dimensional array anyway. It is quite simple. You need to write it down with pencil paper and eraser (the latter being the most important), and you will then find it easy to convert to real code.
Hi jade, and welcome to JavaRanch!
It would be really helpful if you could give us an idea of what you've tried so far and where you're stuck.
My advice for now would be to forget about the input business.
Just write a program that uses a hard-coded set of numbers and write the logic to determine the highest and lowest value.
You could tie that logic to dynamic input at a later stage.
Edit: Ugh, too slow (again)
Build a man a fire, and he'll be warm for a day. Set a man on fire, and he'll be warm for the rest of his life.