io.github.oliviercailloux.samples.coffee.CoffeeMachine Maven / Gradle / Ivy

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package io.github.oliviercailloux.samples.coffee;

/**
 * 
 * A machine that produces coffee of various strength. A strength is a non-negative value. A value
 * of zero for the strength represents no drink at all.
 * 
 *
 * 
 * This interface (naïvely) assumes that a specific quantity of energy is required for producing a
 * coffee. This quantity may depend on the strength of the coffee. (This is naïve because this
 * quantity may in general depend on multiple other factors.)
 * 
 *
 * @author Olivier Cailloux
 *
 */
public interface CoffeeMachine {
  /**
   * Returns the maximal strength that this machine is able to produce.
   *
   * @return a non-negative, finite value.
   */
  public double getMaxStrength();

  /**
   * Returns the time in seconds required for a coffee.
   *
   * @param strength a non-negative value, at most the {@link #getMaxStrength()} value.
   * @return a non-negative value, zero iff the given strength is zero.
   */
  public int getTimeForCoffee(double strength);

  /**
   * 
   * Produces a coffee of the given strength.
   * 
   * 
   * (This increments the number of coffees produced, it does not wait for anything and thus does
   * not block the program.)
   * 
   *
   * @param strength a non-negative value, at most the {@link #getMaxStrength()} value.
   */
  public void produceCoffee(double strength);

  /**
   * Returns the number of coffees that this machine has produced since the beginning of its life.
   * Coffees of strength zero are included.
   *
   * @return a non-negative number.
   */
  public int getNumberOfCoffeesProduced();

  /**
   * Returns the energy spent, in watt times hours, for producing the last coffee.
   *
   * @return a non-negative value, zero iff the last coffee produced had strength zero.
   * @throws IllegalStateException iff this machine has never produced coffee.
   * @see #produceCoffee(double)
   */
  public double getEnergySpent() throws IllegalStateException;
}