If you don’t already have a list of rhyming words, you will just have to enter them all like that (or put them all in a config file of some kind and read that in), but either way you’re just typing them all in.
What you are calling harvesting from rhymezone is called scraping. You can check here: Web scraping with Java for the best way to scrape pages with Java. I would also check with rhymezone about their policy on scraping, or if maybe they provide an API (official way to grab their data).
Also if you’re scraping their website for that kind of information, you will probably want to scrape the data for a word, and store that somewhere, so you aren’t scraping their page every time you want to look up a word.
solved Adding to an arraylist from a website