java 对象作为成员变量

public class Main {
    private int uplimit;
    private int value;

    public Main(int uplimit){
        this.uplimit = uplimit;
    }

    public void tick(){
        value++;
        if(value == uplimit){
            value = 0;
        }
    }

    public int getValue(){ return value; }
    public static void main(String[] args){
        Main d = new Main(24);
        while(true){
            d.tick();
            System.out.println(d.getValue());
        }
    }
}

public class Clock {
    private Main hour = new Main(24);
    private Main minute = new Main(60);

    private void tick(){
        minute.tick();
        if(minute.getValue()==0){
            hour.tick();
        }
    }

    public void show(){
        System.out.printf("%02d:%02d\n", hour.getValue(), minute.getValue());
    }

    public static void main(String[] args) {
        Clock c = new Clock();
        while(true){
            c.tick();
            c.show();
        }
    }
}

运行结果：

05:55
05:56
05:57
05:58
05:59
06:00
06:01
06:02
06:03