juanbecerra0

// Abstract class that other classes can implement
abstract class Item {
  use();
}

// Inherits the 'Item' class's 'use()' method
class Box<T> implements Item {
  // ADT list that can contain other objects
  List<T> contents;

juanbecerra0

void main() {
  print(factorial(1));
  print(factorial(5));
  print(factorial(10));
  print(factorial(20));
}

int factorial(int n) {
  if (n <= 1) { // Base case
    return 1;