Appending a trailing slash if needed I like to overcomplicate things, this is fairly simple though but I would like to keep it simpler without lowering readability. Not just to improve my code but also my self.

private String checkTrailingSlash(String website) {
    if(!website.endsWith("/")){
        website = website + "/";
    }
    return website;
}
You could use a ternary operator to inline the condition into a single return statement:

private String checkTrailingSlash(String website) {
    return website.endsWith("/") ? website : website + "/";
}