Java priority queues and comparable interface

Java priority queues and comparable interface

I've just been learning about priority queues thought i'd try how it
behaves with comparable interface.
import java.util.PriorityQueue;
class kinga implements Comparable<Double> {
double time=909.909;
double d;
public kinga(double a) {
this.d=a;
}
public int compareTo(Double d) {
return Double.compare(d, time);
}
public static void main(String arg[]) {
PriorityQueue<kinga> r=new PriorityQueue<kinga>();
r.add( new kinga(4545.45));
r.add( new kinga(45.4));
r.add( new kinga(1235.45));
System.out.println(r.poll()+" "+r.poll()+" "+r.poll());
}
}
It compiles but gives me Exception in thread "main"
java.lang.ClassCastException: kinga cannot be cast to
java.lang.Double.Whats wrong.Can somebody tell me how comparable and
priority queues work.