interface Comparable {
  public int compareTo (Object that);
}
class Byte implements Comparable {
  private byte value;
  public Byte (byte value) { this.value = value; }
  public byte byteValue () { return value; }
  public int compareTo (Byte that) {
    return this.value - that.value;
  }
  // bridge
  public int compareTo (Object that) {
    return this.compareTo((Byte)that);
  }
}
class Lists {
  public static Comparable max (List xs) {
    Iterator xi = xs.iterator();
    Comparable w = (Comparable)xi.next();
    while (xi.hasNext()) {
      Comparable x = (Comparable)xi.next();
      if (w.compareTo(x) < 0) w = x;
    }
    return w;
  }
}
class Test {
  public static void main (String[] args) {

    // byte list
    List xs = new LinkedList();
    xs.add(new Byte(0)); xs.add(new Byte(1));
    Byte x = (Byte)Lists.max(xs);

    // boolean list
    List ys = new LinkedList();
    ys.add(new Boolean(false)); ys.add(new Boolean(true));
    Boolean y = (Boolean)Lists.max(ys);  // run-time exception
  }
}

Example 3: Declarations for the Comparable interface and the Byte class that implements this interface.