using System;
using System.Collections.Generic;

public class Box<T> {
    private T t; // T stands for "Type"          
    public void set(T t) {
        this.t = t;
    }
    public T get() {
        return t;
    }
}
public class BoxDemo {

  public static void addBox<T>(T u, List<Box<T>> boxes) {
    Box<T> box = new Box<T>();
    box.set(u);
    boxes.Add(box);
  }

  public static void outputBoxes<T>(List<Box<T>> boxes) {
    int counter = 0;
    foreach (Box<T> box in boxes) {
      T boxContents = box.get();
      Console.WriteLine("Box #" + counter + " contains [" +
             boxContents.ToString() + "]");
      counter++;
    }
  }

  public static void Main(String[] args) {
    List<Box<int>> listOfIntegerBoxes =
      new List<Box<int>>();
    BoxDemo.addBox(10, listOfIntegerBoxes);
    BoxDemo.addBox(20, listOfIntegerBoxes);
    BoxDemo.addBox(30, listOfIntegerBoxes);
    BoxDemo.outputBoxes(listOfIntegerBoxes);
  }
}