Method join

solr/solrj/src/java/org/apache/solr/common/util/StrUtils.java:184–198

Creates a backslash escaped string, joining all the items. @see #escapeTextWithSeparator

(Collection<?> items, char separator)

   * @see #escapeTextWithSeparator
   */
  public static String join(Collection<?> items, char separator) {
    if (items == null) return "";
    StringBuilder sb = new StringBuilder(items.size() << 3);
    boolean first = true;
    for (Object o : items) {
      String item = String.valueOf(o);
      if (first) {
        first = false;
      } else {
        sb.append(separator);
      }
      appendEscapedTextToBuilder(sb, item, separator);
    }
    return sb.toString();
  }

  public static List<String> splitWS(String s, boolean decode) {
    ArrayList<String> lst = new ArrayList<>(2);