Static EX - Clock

//----------------------- Clock.java ------------------------

package cls;

public class Clock {

    //Instance variables
    private int hours;
    private int minutes;
    final int MAX_HOURS = 24;
    final int MAX_MINUTES = 60;

    //Static variable
    private static boolean format24 = true;

    public Clock(int hours, int minutes) {
        setHours(hours);
        setMinutes(minutes);
    }

    public Clock(Clock clock) {
        this.hours = clock.hours;
        this.minutes = clock.minutes;
    }

    public int getHours() {
        return hours;
    }

    public void setHours(int hours) {
        if(this.minutes > MAX_HOURS) {
            System.out.println("Hours cannot be more then 24");
        } else {
            this.hours = hours;
        }
    }

    public int getMinutes() {
        return minutes;
    }

    public void setMinutes(int minutes) {
        if(this.minutes > MAX_MINUTES) {
            System.out.println("Minutes cannot be more then 60");
        } else {
            this.minutes = minutes;
        }
    }

    public static boolean isFormat24() {
        return format24;
    }

    public static void setFormat24(boolean format24) {
        Clock.format24 = format24;
    }

    @Override
    public String toString() {
        int h = format24 ? this.hours : this.hours % 12;
        String m = (minutes < 10) ? "0" + this.minutes : "" + this.minutes;
        return (h < 10) ? "0" + h + ":" + m : h + ":" + m;
    }
}

//------------------------- Tester class -------------------------------

package tester;

import cls.Clock;

public class ClockTester {

    public static void main(String[] args) {
        Clock clock = new Clock(15, 40);
        System.out.println(clock.toString());
        clock.setHours(40);
        Clock.setFormat24(false);
        System.out.println(clock.toString());
    }
}