var list = ['a', 'b', 'c', 'd'];
//index of last two element
final indexOfsecondToLast = list.length - 2;
//index of last element
final indexOfLast = list.length - 1;
//last element in array
final LastElement = list.elementAt(list.length - 1);
//last two element in an array
final secondToLastElement = list.elementAt(list.length - 2);