Fastest way to put contents of Set to a single String with words separated by a whitespace?

Question

I have a few Sets and want to transform each of these into a single String where each element of the original Set is sep

Answer 1

I use this method:

public static String join(Set set, String sep) {
    String result = null;
    if(set != null) {
        StringBuilder sb = new StringBuilder();
        Iterator it = set.iterator();
        if(it.hasNext()) {
            sb.append(it.next());
        }
        while(it.hasNext()) {
            sb.append(sep).append(it.next());
        }
        result = sb.toString();
    }
    return result;
}