How to submit a solution in Java

Could anyone let me know how to submit a solution in Java? The youtube link provided doesn’t seem to work. A small example would be helpful

Just click “Submit” and in the drop down select “javac-…” .

You have to take input from console and write output to console .
eg . See the below question

and the solution for it in JAVA .

did that, i am a bit confused about the way in which i have to write programs…especially when the program has to take input from the user…should i take input from console or do i just write methods assuming that the test cases will call the methods that I have written?.. A sample file which takes input and displays the input will be useful…