/** * The MIT License * Copyright (c) 2014-2016 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.value.object; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * A Value Object are objects which follow value semantics rather than reference semantics. This * means value objects' equality are not based on identity. Two value objects are equal when they * have the same value, not necessarily being the same object.. * * Value Objects must override equals(), hashCode() to check the equality with values. * Value Objects should be immutable so declare members final. * Obtain instances by static factory methods. * The elements of the state must be other values, including primitive types. * Provide methods, typically simple getters, to get the elements of the state. * A Value Object must check equality with equals() not == * * For more specific and strict rules to implement value objects check the rules from Stephen * Colebourne's term VALJO : http://blog.joda.org/2014/03/valjos-value-java-objects.html */ public class App { private static final Logger LOGGER = LoggerFactory.getLogger(App.class); /** * This practice creates three HeroStats(Value object) and checks equality between those. */ public static void main(String[] args) { HeroStat statA = HeroStat.valueOf(10, 5, 0); HeroStat statB = HeroStat.valueOf(10, 5, 0); HeroStat statC = HeroStat.valueOf(5, 1, 8); LOGGER.info(statA.toString()); LOGGER.info("Is statA and statB equal : {}", statA.equals(statB)); LOGGER.info("Is statA and statC equal : {}", statA.equals(statC)); } }