String join(
[String separator = ""]
)

Converts each element to a String and concatenates the strings.

Iterates through elements of this iterable, converts each one to a String by calling Object.toString, and then concatenates the strings, with the separator string interleaved between the elements.

Source

/**
 * Converts each element to a [String] and concatenates the strings.
 *
 * Iterates through elements of this iterable,
 * converts each one to a [String] by calling [Object.toString],
 * and then concatenates the strings, with the
 * [separator] string interleaved between the elements.
 */
String join([String separator = ""]) {
  StringBuffer buffer = new StringBuffer();
  buffer.writeAll(this, separator);
  return buffer.toString();
}