HashSet, from URL to HashSet JAVA

in the task I have to read a list of names stored in the URL in the column. I have to read them from the URL (I have already done this) and then I am using a set to draw 15 names without repeat (random) names. I have no idea how to do it, I was looking at google, but unfortunately I did not find the answer to my problem. I am asking for help and guidance