// Example 27 from page 23 of Java Precisely second edition (The MIT Press 2005)
// Author: Peter Sestoft (sestoft@itu.dk)


abstract class Vessel {
  double contents;
  abstract double capacity();
  void fill(double amount) { contents = Math.min(contents + amount, capacity()); }
}

class Tank extends Vessel {
  double length, width, height;

  Tank(double length, double width, double height) 
  { this.length = length; this.width = width; this.height = height; }

  double capacity() { return length * width * height; }

  public String toString() 
  { return "tank (" + length + ", " + width + ", " + height + ")"; }
}

class Cube extends Tank {
  Cube(double side) { super(side, side, side); }
  public String toString() { return "cube (" + length + ")"; }
}

class Barrel extends Vessel {
  double radius, height;
  Barrel(double radius, double height) { this.radius = radius; this.height = height; }
  double capacity() { return height * Math.PI * radius * radius; }
  public String toString() { return "barrel (" + radius + ", " + height + ")"; }
}