/** * The MIT License * Copyright (c) 2014 Ilkka Seppälä * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ package com.iluwatar.privateclassdata; /** * * The Private Class Data design pattern seeks to reduce exposure of attributes by limiting their * visibility. It reduces the number of class attributes by encapsulating them in single data * object. It allows the class designer to remove write privilege of attributes that are intended to * be set only during construction, even from methods of the target class. *
* In the example we have normal {@link Stew} class with some ingredients given in constructor. Then * we have methods to enumerate the ingredients and to taste the stew. The method for tasting the * stew alters the private members of the {@link Stew} class. * * The problem is solved with the Private Class Data pattern. We introduce {@link ImmutableStew} * class that contains {@link StewData}. The private data members of {@link Stew} are now in * {@link StewData} and cannot be altered by {@link ImmutableStew} methods. * */ public class App { /** * Program entry point * * @param args command line args */ public static void main(String[] args) { // stew is mutable Stew stew = new Stew(1, 2, 3, 4); stew.mix(); stew.taste(); stew.mix(); // immutable stew protected with Private Class Data pattern ImmutableStew immutableStew = new ImmutableStew(2, 4, 3, 6); immutableStew.mix(); } }