code: public static String join(Object[] array, String separator) {
  		return org.apache.commons.lang3.StringUtils.join(array, separator);
  	}
docs: <p>
  Joins the elements of the provided array into a single String containing
  the provided list of elements.
  </p>
  <p>
  No delimiter is added before or after the list. A null separator is the
  same as an empty String (""). Null objects or empty strings within the
  array are represented by empty strings.
  </p>
  
  <pre>
  StringUtils.join(null, *)                = null
  StringUtils.join([], *)                  = ""
  StringUtils.join([null], *)              = ""
  StringUtils.join(["a", "b", "c"], "--")  = "a--b--c"
  StringUtils.join(["a", "b", "c"], null)  = "abc"
  StringUtils.join(["a", "b", "c"], "")    = "abc"
  StringUtils.join([null, "", "a"], ',')   = ",,a"
  </pre>
  
  
  @param array
  the array of values to join together, may be null
  @param separator
  the separator character to use, null treated as ""
  @return the joined String, null if null array input