public class Interfaces {
  public static void main(String[] args) {
    Coin[] c = {new Penny(), new Dime(), new Dime() };
    int pocket = 0;
    for (int i=0; i<c.length; i++)
      pocket += c[i].getValue();
    System.out.println(pocket); 
  }
}

interface Coin {
  public int getValue();
}

class Penny implements Coin {
  public int getValue() { return 1; }
}

class Dime implements Coin {
  public int getValue() { return 10; }
}