docs: public static String join(final Object array, final String separator) {
  		$.checkNotEmpty(array);
  		Class<?> arrayType = array.getClass();
  		Preconditions.checkArgument(arrayType.isArray(), "parameter array must be Array: %s", array);
  
  		StringBuffer sb = new StringBuffer();
  		sb.append(Array.get(array, 0));
  
  		int length = Array.getLength(array);
  		for (int i = 1; i < length; i++) {
  			sb.append(separator).append(Array.get(array, i));
  		}
  
  		return sb.toString();
  	}