public class ClockDisplay
{
    private NumberDisplay hours;
    private NumberDisplay minutes;
    private String displayString;    // simulates the actual display
 
    //clockdisplay constuctor
    public ClockDisplay()
    {
        hours = new NumberDisplay(24);
        minutes = new NumberDisplay(60);
        updateDisplay();
    }
    //clockdisplay constuctor
    public ClockDisplay(int hour, int minute)
    {
        hours = new NumberDisplay(24);
        minutes = new NumberDisplay(60);
        setTime(hour, minute);
    }
 
    /**
     * This method should get called once every minute - it makes
     * the clock display go one minute forward.
     */
    public void timeTick()
    {
        minutes.increment();
        if(minutes.getValue() == 0) {  // it just rolled over!
            hours.increment();
        }
        updateDisplay();
    }
 
    /**
     * Set the time of the display to the specified hour and
     * minute.
     */
    public void setTime(int hour, int minute)
    {
        hours.setValue(hour);
        minutes.setValue(minute);
 
        if (hour == 12)
        {
            hours.setValue(00);
            minutes.setValue(30);
            hours.increment();
            minutes.increment();
            updateDisplay();
        }
 
        //ex 3.31 i have to do an if statement
        //i have to modify it this method.
        updateDisplay();
    }
 
    /**
     * Return the current time of this display in the format HH:MM.
     */
    public String getTime()
    {
        return displayString;
    }
 
    /**
     * Update the internal string that represents the display.
     * 
     * accommodate the updateDisplay to print 4:23 when the internal
     * value is 16:23 date 10-21-09
     */
    private void updateDisplay()   //int hour, int minute
    {
        //hours.setValue(hour);
        //minutes.setValue(minute);
 
        //computer made
        displayString = hours.getDisplayValue() + ":" + 
                        minutes.getDisplayValue();
 
        //programmer made    
        //error:Incomparable types:NumberDisplay and int
        if (hours == 16 && minutes == 23)
        {
            hour.setValue(4);
            mintues.setValue(23);
            hours.increment();
            minutes.increment();
        }        
    }
}