provides a string joining implementation for Java < 8

join.java

/**
 * Joins the collection with string 'delimiter'. Somehow this function
 * was overlooked in the stdlib until Java 8.
 * <p>
 * delimiter and collection must not be null.
 */
private static <T> String join(String delimiter, Collection<T> collection) {
    // PRECONDITION delimiter and collection must not be null
    StringBuilder result = new StringBuilder();
    Iterator<T> iter = collection.iterator();
    while (iter.hasNext()) {
        result.append(iter.next());
        if (iter.hasNext())
            result.append(delimiter);
    }
    return result.toString();
}