coffee.java

// see repo for full code

boolean milk;    
boolean soy;    
boolean mocha;    
boolean whip;

// and their getters and setters

public int cost() {
  int total = 0;
  if (isMilk()) {
    total += MILK_COST;
  }
  if (isSoy()) {
    total += SOY_COST;
  }
  if (isMocha()) {
    total += MOCHA_COST;
  }
  if (isWhip()) {
    total += WHIP_COST;
  }
  return total;
}