Programming-Idioms

int n = a.length - 1;
String s = switch (n) {
    case 0 -> a[0];
    case 1 -> a[0] + " and " + a[1];
    default -> {
        s = join(", ", copyOfRange(a, 0, n));
        yield s + ", and " + a[n];
    }
};

String s = format("{0,list}", a);

  if Length(a) > 1 then
  begin
    s := String.Join(', ', a, 0, Length(a)-1);
    s := s + ' and ' + a[High(a)]
  end
  else
  begin
    if Length(a) > 0 then
      s := a[0]
    else
      s :='';
  end;

match len(a):
    case 1: s = a[0]
    case 2: s = ' and '.join(a)
    case _:
        s = ', '.join(a[:-1])
        s = s + ', and ' + a[-1]

class List:
    def __init__(self):
        self.m = []
    def apply(self, /, *x, y='', z=''):
        self.m.append((x, y, z))
    def parse(self, x):
        x = [*map(str, x)]
        for a, y, z in self.m:
            for i in a: x[i] = y + x[i] + z
        return ''.join(x)
x = List()
match n := len(a):
    case 1: ...
    case 2: x.apply(0, z=' and ')
    case _:
        x.apply(*range(n - 1), z=', ')
        x.apply(-1, y='and ')
s = x.parse(a)

remainder, last = a[..-2], a[-1]
s = remainder.join(", ") + "#{' and ' unless remainder.empty?}" + last.to_s