parquet-common/src/main/java/org/apache/parquet/Strings.java
public static String join(Iterable<String> s, String on) {
    return join(s.iterator(), on);
  }
public static String join(Iterable<String> s, String on) {
    return join(s.iterator(), on);
  }
Join an Iterable of Strings into a single string with a delimiter.
For example, join(Arrays.asList("foo","","bar","x"), "|") would return
"foo||bar|x"

@param s an iterable of strings
@param on the delimiter
@return a single joined string