public static String join(String separator, Collection<String> stringsToJoin) {
        StringBuilder builder = new StringBuilder();
        // Check if there is at least 1 element then use do/while to avoid trailing separator
        int index = stringsToJoin.size();
        for (String str : stringsToJoin) {
            index--;
            if (str != null) {
                builder.append(str);
                if (index > 0) {
                    builder.append(separator);
                }
            }
        }
        return builder.toString();
    }
public static String join ( String separator , Collection < String > stringsToJoin ) { StringBuilder builder = new StringBuilder ( ) ; int index = stringsToJoin . size ( ) ; for ( String str : stringsToJoin ) { index -- ; if ( str != null ) { builder . append ( str ) ; if ( index > 0 ) { builder . append ( separator ) ; } } } return builder . toString ( ) ; }
Utility to join strings with a separator. Skips null strings and does not append a trailing
separator.

@param separator     the string to use to separate the entries
@param stringsToJoin the strings to join together
@return the joined string