How to get a boolean from a page, and set it to another

I'm making an Java Program in which I need to do something based on a boolean in a HTML page.

I need to know how to retrieve the boolean (it's a page with one line, it being true or false), and after retrieving, how to set it's value? My program needs to access an external webpage, which I have the domain and control over. I can't find a way to read the lines on the webpage, nor to open the html File and set the boolean

I can retrieve the boolean using a BufferedReader, but don't have an idea on how to access the file via FTP and editing it