[hardwired]

exception in thread main java.lang.nosuchmethoderror
Means that the jvm could not find a main method in the class.

Code:

public class ClockRx {
    ... everything same as before ...
    /** add a main method */
    public static void main(String[] args) {
        ClockRc clock = new ClockRx();
        // now you can access fields and call
        // methods in the ClockRx class.
    }
}