Java初学習-Javaでのコピー構築関数

//Example：
//1.Clock ：
public class Clock {
 private int hour;
 private int minute;
 private int second;
 
 public Clock(){
  setTime(0,0,0);
 }
 
 public Clock(int h,int m,int s){
  setTime(h,m,s);
 }
 
 /*        */
 public Clock(Clock clock){
  this.hour=clock.hour;
  this.minute=clock.minute;
  this.second=clock.second;
 }
 
 public int getHour() {
  return hour;
 }
 public int getMinute() {
  return minute;
 }
 public int getSecond() {
  return second;
 }
 public void setTime(int h,int m,int s){
  if(h>=0 && h<24)
   this.hour=h;
  else
   this.hour=0;
  
  if(m>=0 && m<60)
   this.minute=m;
  else
   this.minute=0;
  
  if(s>=0 && s<60)
   this.second=s;
  else
   this.second=0;
 }
 
 public void printTime(){
  if(this.hour<10)
   System.out.print("0");
  System.out.print(this.hour+":");
  
  if(this.minute<10)
   System.out.print("0");
  System.out.print(this.minute+":");
  
  if(this.second<10)
   System.out.print("0");
  System.out.println(this.second);
 }
}
//2.main  ：
public class Program {
 public static void main(String[] args) {
  Clock c1=new Clock(6,43,23);
  Clock c2=new Clock(c1);//        
  c1.printTime();
  c2.printTime();
 }
}
//3.    ：
06:43:23
06:43:23