code: public String join(String separator) throws JSONException {
  		int len = this.length();
  		StringBuilder sb = new StringBuilder();
  
  		for (int i = 0; i < len; i += 1) {
  			if (i > 0) {
  				sb.append(separator);
  			}
  			sb.append(JSONObject.valueToString(this.list.get(i)));
  		}
  		return sb.toString();
  	}
docs: Make a string from the contents of this JSONArray. The
  <code>separator</code> string is inserted between each element. Warning:
  This method assumes that the data structure is acyclical.
  
  @param separator A string that will be inserted between the elements.
  @return a string.
  @throws JSONException If the array contains an invalid number.