/**
  * Adds the connections between two boxes.
  *
  * @param nameBox1 Name of the upper box.
  * @param nameBox2 Name of the lower box.
  */
 public void addConnection(String nameBox1, String nameBox2) {
   for (Box box1 : this.boxes) {
     if (box1.getName().equals(nameBox1)) {
       for (Box box2 : this.boxes) {
         if (box2.getName().equals(nameBox2)) {
           box1.addBoxUnder(box2);
           box2.addBoxAbove(box1);
         }
       }
     }
   }
 }