Example of how to use a Java interface as a type

Dialer.java

// note that all the static keywords on the methods and interface are just b/c I'm implementing these as belonging to the Dialer class
// rather than as belonging to an instance of Dialer
// if you aren't nesting them like this (which you prbably aren't) then you won't need to do that

public class Dialer {

  public abstract static interface Dialable { public abstract String dial(); }

  public static class Phone implements Dialable {
    private String number;
    public Phone(String number) { this.number = number; }
    public String dial() { return "Now dialing " + number; }
  }

  // apparently there is some retarted bullshit where inner classes can't have static vars
  public static class Clock implements Dialable {
    private int face;
    public Clock(int face) { this.face = face; }
    public String dial() { 
      return "This clock has a " + new String[]{ "Sun" , "Twelve Hour" ,"Twenty Four Hour" }[face] + " Dial";
    }
  }
  
  
  // =====  THE Dialer CLASS ITSELF  =====
  
  public static void main(String[] args) {
    Dialable[] dialables = new Dialable[]{ new Phone("123-456") , new Clock(0) , new Clock(1) , new Phone("938-9582") , new Clock(2) };
    new Dialer(dialables).printDialables();
  }
  
  private Dialable[] dialables;
  public Dialer(Dialable[] dialables) { this.dialables = dialables; }
  
  public void printDialables() {
    for( Dialable dialable : dialables ) System.out.println( dialable.dial() );
  }
  
}

Great