Simple demo of avoiding side-effects by using Object.clone : Clone « Class « Java






Simple demo of avoiding side-effects by using Object.clone

Simple demo of avoiding side-effects by using Object.clone
      

/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * Java, the Duke mascot, and all variants of Sun's Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun's, and James Gosling's,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */
import java.util.*;

/**
 * Simple demo of avoiding side-effects by using Object.clone()
 * to duplicate an object before passing it to your enemy's methods.
 * Cloneable is a "marker" interface: it has no methods, but is tested
 * for by Object.clone. If you implement it, you tell Object.clone that
 * your data is stable enough that field-by-field copy is OK.
 */
class Enemy {
  public void munge(SideEffects md) {
    System.out.println("Object is " + md);
    md.year = 0;
    md.td.setYear(71);    // Ignore deprecation warnings
  }
}

public class SideEffects implements Cloneable {
  /** When we clone a "SideEffects", this REFERENCE gets cloned */
  public Date td;  
  /** When we clone a "SideEffects", this integer does NOT get cloned */
  volatile int year;

  public static void main(String[] argv) throws CloneNotSupportedException {
    new SideEffects().process();
  }

  SideEffects() {
    td = new Date();  // today
    year = td.getYear();
  }

  public void process() throws CloneNotSupportedException {
    Enemy r = new Enemy();
    System.out.println("We have seen the enemy, and he is " + r);
    System.out.println("Today is " + td + "; nice weather, isn't it?");
    System.out.println("And the year is " + year);
    r.munge((SideEffects)this.clone());
    System.out.println("Why, I believe it is now " + td);
    if (year == 0)    // should not happen!!
      System.out.println("** PANIC IN YEAR ZERO **");
    System.out.println("But wait, the year is still " + year);
    r.munge(this);
    System.out.println("Now I'm certain that it's " + td);
    System.out.println("Now the year is  " + year);
  }
}


           
         
    
    
    
    
    
  








Related examples in the same category

1.A Cloning Example
2.Class is declared to be cloneable.
3.Arrays are automatically cloneable
4.Clone objects
5.Creating a Deep Copy
6.Shallow Copy TestShallow Copy Test
7.Deep Copy TestDeep Copy Test
8.Uses serialization to perform deep copy cloning.
9.Tests cloning to see if destination of references are also clonedTests cloning to see if destination of references are also cloned
10.Creating local copies with cloneCreating local copies with clone
11.You can insert Cloneability at any level of inheritance
12.Cloning a composed objectCloning a composed object
13.Serializable and cloneSerializable and clone
14.Go through a few gyrations to add cloning to your own classGo through a few gyrations to add cloning to your own class
15.Checking to see if a reference can be clonedChecking to see if a reference can be cloned
16.The clone operation works for only a few items in the standard Java libraryThe clone operation works for only a few items in the standard Java library
17.Demonstration of cloning
18.Clone an object with clone method from parent
19.Manipulate properties after clone operation
20.Deep clone ObjectDeep clone Object
21.Serializable Clone
22.Utility for object cloning
23.Clone Via Serialization
24.Clone demo
25.Deep clone serializing/de-serializng Clone
26.Implements a pool of internalized objects
27.A collection of utilities to workaround limitations of Java clone framework
28.This program demonstrates cloning
29.Returns a copy of the object, or null if the object cannot be serialized.Returns a copy of the object, or null if the object cannot be serialized.
30.Deep-copies the values from one object to the other
31.Object Deep copy