clonetest.java

适合处学者JAVA者的代码

/**
   @version 1.00 2000-04-13
   @author Cay Horstmann
*/

import java.util.*;

public class CloneTest
{  
   public static void main(String[] args)
   {  
      Employee original = new Employee("John Q. Public", 50000); 
      original.setPayDay(2000, 1, 1);
      Employee copy = (Employee)original.clone();
      copy.raiseSalary(10);
      copy.addPayDay(14);
      System.out.println("original=" + original);
      System.out.println("copy=" + copy);
   }
}

/**
   An employee class with a mutable payDay field
*/
class Employee implements Cloneable
{  
   public Employee(String n, double s)
   {  
      name = n;
      salary = s;
   }

   public Object clone()
   {
      try
      {
         // call Object.clone()
         Employee cloned = (Employee)super.clone(); 

         // clone mutable fields
         cloned.payDay = (GregorianCalendar)payDay.clone();
         
         return cloned;
      }
      catch (CloneNotSupportedException e) { return null; }
   }

   /**
      Set the pay day to a given date
      @param year the year of the pay day
      @param month the month of the pay day
      @param day the day of the pay day
   */
   public void setPayDay(int year, int month, int day)
   {
      payDay = new GregorianCalendar(year, month - 1, day);
   }


   /**
      Add a number of days to the pay day (e.g. add 14 days)
      @param days the number of days to add
   */
   public void addPayDay(int days)
   {
      payDay.add(Calendar.DAY_OF_MONTH, days);
   }

   public Date getPayDay()
   {
      return payDay.getTime();
   }

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

   public String toString()
   {
      return "Employee[name=" + name
         + ",salary=" + salary
         + ",payDay=" + getPayDay()
         + "]";
   }

   private String name;
   private double salary;
   private GregorianCalendar payDay;
}