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* feat: implement Immutable pattern #3448 Add immutable/ module with ImmutableUser (final class, defensive copy, withAge wither method), App demo, JUnit 5 tests, PlantUML diagram, and README following project conventions. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> * feat: add withName and withRoles wither methods to ImmutableUser #3448 Every field now has a corresponding wither for consistency. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> * fix: add junit-jupiter-api dependency to immutable module #3448 Required for @Test annotations and assert methods in test code. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> --------- Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.immutable;
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import java.util.List;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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/**
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* The Immutable pattern ensures that an object's state cannot be changed after construction.
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*
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* <p>In this example, {@link ImmutableUser} demonstrates the pattern: all fields are final, the
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* mutable {@code roles} list is defensively copied, and any state change produces a brand-new
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* instance via {@link ImmutableUser#withAge(int)}.
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*/
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public class App {
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private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
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/**
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* Program entry point.
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*
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* @param args command line args
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*/
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public static void main(String[] args) {
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var alice = new ImmutableUser("Alice", 30, List.of("admin", "user"));
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LOGGER.info("Original user: {}", alice);
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var olderAlice = alice.withAge(31);
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LOGGER.info("Updated user (new object): {}", olderAlice);
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LOGGER.info("Original is unchanged: {}", alice);
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// Demonstrate defensive copy: mutating the source list does not affect alice
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var mutableRoles = new java.util.ArrayList<>(List.of("viewer"));
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var bob = new ImmutableUser("Bob", 25, mutableRoles);
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mutableRoles.add("editor");
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LOGGER.info("Bob's roles (unchanged despite external list mutation): {}", bob.getRoles());
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}
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}
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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.immutable;
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import java.util.List;
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/**
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* An immutable representation of a user.
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*
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* <p>All fields are final and set only at construction time. The {@code roles} list is defensively
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* copied to prevent external mutation. Any "modification" produces a new {@link ImmutableUser}
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* instance, leaving the original unchanged.
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*/
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public final class ImmutableUser {
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private final String name;
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private final int age;
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private final List<String> roles;
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/**
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* Constructs an {@link ImmutableUser} with the given attributes.
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*
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* @param name the user's name
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* @param age the user's age
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* @param roles the user's roles; copied defensively so external changes have no effect
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*/
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public ImmutableUser(String name, int age, List<String> roles) {
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this.name = name;
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this.age = age;
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this.roles = List.copyOf(roles);
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}
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/**
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* Returns the user's name.
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*
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* @return name
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*/
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public String getName() {
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return name;
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}
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/**
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* Returns the user's age.
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*
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* @return age
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*/
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public int getAge() {
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return age;
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}
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/**
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* Returns an unmodifiable view of the user's roles.
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*
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* @return roles
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*/
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public List<String> getRoles() {
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return roles;
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}
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/**
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* Returns a new {@link ImmutableUser} identical to this one but with the given name.
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*
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* @param newName the new name value
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* @return a new instance with the updated name
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*/
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public ImmutableUser withName(String newName) {
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return new ImmutableUser(newName, this.age, this.roles);
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}
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/**
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* Returns a new {@link ImmutableUser} identical to this one but with the given age.
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*
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* @param newAge the new age value
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* @return a new instance with the updated age
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*/
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public ImmutableUser withAge(int newAge) {
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return new ImmutableUser(this.name, newAge, this.roles);
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}
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/**
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* Returns a new {@link ImmutableUser} identical to this one but with the given roles.
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*
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* @param newRoles the new roles; copied defensively
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* @return a new instance with the updated roles
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*/
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public ImmutableUser withRoles(List<String> newRoles) {
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return new ImmutableUser(this.name, this.age, newRoles);
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}
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@Override
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public String toString() {
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return "ImmutableUser{name='" + name + "', age=" + age + ", roles=" + roles + '}';
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}
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}
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@@ -0,0 +1,123 @@
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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.immutable;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertNotSame;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import java.util.ArrayList;
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import java.util.List;
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import org.junit.jupiter.api.Test;
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class ImmutableUserTest {
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@Test
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void constructorSetsAllFields() {
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var user = new ImmutableUser("Alice", 30, List.of("admin"));
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assertEquals("Alice", user.getName());
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assertEquals(30, user.getAge());
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assertEquals(List.of("admin"), user.getRoles());
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}
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@Test
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void withAgeReturnsNewObjectWithUpdatedAge() {
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var original = new ImmutableUser("Alice", 30, List.of("admin"));
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var updated = original.withAge(31);
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assertEquals(31, updated.getAge());
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assertEquals("Alice", updated.getName());
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assertEquals(original.getRoles(), updated.getRoles());
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}
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@Test
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void withAgeDoesNotMutateOriginal() {
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var original = new ImmutableUser("Alice", 30, List.of("admin"));
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original.withAge(99);
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assertEquals(30, original.getAge());
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}
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@Test
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void withAgeReturnsDistinctInstance() {
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var original = new ImmutableUser("Alice", 30, List.of("admin"));
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var updated = original.withAge(31);
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assertNotSame(original, updated);
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}
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@Test
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void defensiveCopyPreventsExternalListMutation() {
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var mutableRoles = new ArrayList<>(List.of("viewer"));
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var user = new ImmutableUser("Bob", 25, mutableRoles);
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mutableRoles.add("editor");
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assertEquals(List.of("viewer"), user.getRoles());
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}
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@Test
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void getRolesReturnsUnmodifiableList() {
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var user = new ImmutableUser("Bob", 25, List.of("viewer"));
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assertThrows(UnsupportedOperationException.class, () -> user.getRoles().add("editor"));
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}
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@Test
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void withNameReturnsNewObjectWithUpdatedName() {
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var original = new ImmutableUser("Alice", 30, List.of("admin"));
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var updated = original.withName("Bob");
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assertEquals("Bob", updated.getName());
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assertEquals(30, updated.getAge());
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assertEquals(original.getRoles(), updated.getRoles());
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}
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@Test
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void withNameDoesNotMutateOriginal() {
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var original = new ImmutableUser("Alice", 30, List.of("admin"));
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original.withName("Bob");
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assertEquals("Alice", original.getName());
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}
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@Test
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void withRolesReturnsNewObjectWithUpdatedRoles() {
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var original = new ImmutableUser("Alice", 30, List.of("admin"));
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var updated = original.withRoles(List.of("viewer", "editor"));
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assertEquals(List.of("viewer", "editor"), updated.getRoles());
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assertEquals("Alice", updated.getName());
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assertEquals(30, updated.getAge());
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}
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@Test
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void withRolesDoesNotMutateOriginal() {
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var original = new ImmutableUser("Alice", 30, List.of("admin"));
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original.withRoles(List.of("viewer"));
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assertEquals(List.of("admin"), original.getRoles());
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}
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}
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