用Java 设计一个时钟程序，包含4个类：clock、hour、minute、second，clock类内实现以下三个函数：Time() 显示当前时间，格式HH:mm:SS，tick()每秒执行一次，完成时间经过1秒的功能，set(int HH,int mm,int SS)将时间设置为指定的时分秒，所有的属性都必须为private

下面是一个可能的实现：

Clock.java

public class Clock {
    private Hour hour;
    private Minute minute;
    private Second second;

    public Clock() {
        this.hour = new Hour();
        this.minute = new Minute();
        this.second = new Second();
    }

    public void setTime(int HH, int mm, int SS) {
        this.hour.set(HH);
        this.minute.set(mm);
        this.second.set(SS);
    }

    public void tick() {
        this.second.increment();
        if (this.second.get() == 0) {
            this.minute.increment();
            if (this.minute.get() == 0) {
                this.hour.increment();
            }
        }
    }

    public String getTime() {
        return String.format("%02d:%02d:%02d", this.hour.get(), this.minute.get(), this.second.get());
    }
}

Hour.java

public class Hour {
    private int value;

    public Hour() {
        this.value = 0;
    }

    public int get() {
        return this.value;
    }

    public void set(int value) {
        this.value = value % 24;
    }

    public void increment() {
        this.value = (this.value + 1) % 24;
    }
}

Minute.java

public class Minute {
    private int value;

    public Minute() {
        this.value = 0;
    }

    public int get() {
        return this.value;
    }

    public void set(int value) {
        this.value = value % 60;
    }

    public void increment() {
        this.value = (this.value + 1) % 60;
    }
}

Second.java

public class Second {
    private int value;

    public Second() {
        this.value = 0;
    }

    public int get() {
        return this.value;
    }

    public void set(int value) {
        this.value = value % 60;
    }

    public void increment() {
        this.value = (this.value + 1) % 60;
    }
}

使用示例：

Clock clock = new Clock();
clock.setTime(23, 59, 59);
for (int i = 0; i < 5; i++) {
    clock.tick();
    System.out.println(clock.getTime());
}

输出：

00:00:00
00:00:01
00:00:02
00:00:03
00:00:04