例子:

class Employee implements Cloneable

{

        private String name;

        private double salary;

        private Date birthday;

        // setter �getter

        public Object clone()

        {

                try

                {

                        Employee cloned = (Employee ) super.clone();

                        cloned.birthday = (Date) birthday.clone();

                }catch(CloneNotSupportedException e) {

                return null;

                }

        }

}

 说明åQ?/p>

1åQ‰Employee 必须实现 Cloneable接口 åQˆæ ‡å¿—接口）

     标志接口åQšå®Œå…¨çš„½IºæŽ¥å£ã€‚这里的作用是告诉ＪåQӞ݋åQŒç±»çš„设计者理解了cloneable()æ–ÒŽ(gu¨©)³•åQŒå¯ä»¥é€šè¿‡isInstanceOf˜q›è¡Œ˜qè¡Œæ—¶æ£€æŸ¥ã€?/p>

2åQ‰è¦†å†™çš„clone()æ–ÒŽ(gu¨©)³•å¿…须定义为public (原是protected)

3åQ‰clone()æ–ÒŽ(gu¨©)³•ä½“å¿…™åÕdœ¨try-catch {}中，捕获处理CloneNotSupportedException 。（防止¾cÀL²¡æœ‰å®žçŽ°Cloneable接口åQŒæ­£¼‹®å®žçŽîCº†æ·±å…‹éš†çš„话，˜q™ä¸ªå¼‚常肯定不会(x¨¬)抛出åQ?/p>

ｐｓ.   JDK中，StringBuffer没有覆写clone()æ–ÒŽ(gu¨©)³•åQŒè™½ç„¶å®ƒ¼‹®å®ž¾l§æ‰¿äº†Objectçš„clone()åQŒä½†åœ¨å®žé™…应用中åQŒã€€å› äØ“(f¨´)StringBuffer¾lä¸ä¼?x¨¬)有子类åQŒè€Œä¸”是在JDK外ä‹É用StringBufferåQŒæ‰€ä»¥è¢«protected界定的clone()æ–ÒŽ(gu¨©)³•æ˜¯å®Œå…¨ä¸å¯è§çš„！

 

æ–ÒŽ(gu¨©)³•åQˆå››åQ‰ä‹É用序列化˜q›è¡Œå…‹éš†

˜q™ç§æ–ÒŽ(gu¨©)³•æ¶‰åŠ(qi¨¢ng)IO操作åQŒæ‰€ä»¥ç›¸å¯ÒŽ(gu¨©)¥è®²è¦æ¯”方法（三）慢．

import java.io.*;
import java.util.*;

public class SerialCloneTest
{ 
   public static void main(String[] args)
   { 
      Employee harry = new Employee("Harry Hacker", 35000,
         1989, 10, 1);
      // clone harry
      Employee harry2 = (Employee)harry.clone();

      // mutate harry
      harry.raiseSalary(10);

      // now harry and the clone are different
      System.out.println(harry);
      System.out.println(harry2);
   }
}

/**
   A class whose clone method uses serialization.
*/
class SerialCloneable implements Cloneable, Serializable
{ 
   public Object clone()
   { 
      try
      { 
         // save the object to a byte array
         ByteArrayOutputStream bout = new
            ByteArrayOutputStream();
         ObjectOutputStream out
            = new ObjectOutputStream(bout);
         out.writeObject(this);
         out.close();

         // read a clone of the object from the byte array
         ByteArrayInputStream bin = new
            ByteArrayInputStream(bout.toByteArray());
         ObjectInputStream in = new ObjectInputStream(bin);
         Object ret = in.readObject();
         in.close();

         return ret;
      } 
      catch (Exception e)
      { 
         return null;
      }
   }
}

/**
   The familiar Employee class, redefined to extend the
   SerialCloneable class.
*/
class Employee extends SerialCloneable
{ 
   public Employee(String n, double s,
      int year, int month, int day)
   { 
      name = n;
      salary = s;
      GregorianCalendar calendar
         = new GregorianCalendar(year, month - 1, day);
         // GregorianCalendar uses 0 for January
      hireDay = calendar.getTime();
   }

   public String getName()
   { 
      return name;
   }

   public double getSalary()
   { 
      return salary;
   }

   public Date getHireDay()
   { 
      return hireDay;
   }

   public void raiseSalary(double byPercent)
   { 
      double raise = salary * byPercent / 100;
      salary += raise;
   }

   public String toString()
   { 
      return getClass().getName()
         + "[name=" + name
         + ",salary=" + salary
         + ",hireDay=" + hireDay
         + "]";
   }

   private String name;
   private double salary;
   private Date hireDay;
}

 

 æ–ÒŽ(gu¨©)³•åQˆäº”åQ?其他æ–ÒŽ(gu¨©)³•

可以通过java的反ž®„机制定义一个类ä¼égºŽå¯¹è±¡åºåˆ—化的万能克隆。改˜q›åŽå†è„“(chu¨¤ng)上来ã€?/p>