Implement Entity Component System (ECS) architecture

entity-component-system/etc/entity-component-system.urm.puml

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+@startuml
+package com.iluwatar {
+  class App {
+    + App()
+    + main(args : String[]) {static}
+  }
+  abstract class Component {
+    - isEnabled : boolean
+    - name : String
+    - parent : Entity
+    + Component()
+    + getEnabled() : boolean
+    + getName() : String
+    + getParent() : Entity
+    + setEnabled(isEnabled : boolean)
+    + setName(name : String)
+    + setParent(parent : Entity)
+    + update(float) {abstract}
+  }
+  class Entity {
+    - children : List<Entity>
+    - components : List<Component>
+    - entityId : UUID
+    - gameSystem : GameSystem
+    - isEnabled : boolean
+    - name : String
+    - parent : Entity
+    - transform : TransformComponent
+    + Entity(entityName : String)
+    + addChild(child : Entity)
+    + addComponent(component : Component)
+    + getChildren() : List<Entity>
+    + getComponent(componentName : String) : Component
+    + getEntityId() : UUID
+    + getGameSystem() : GameSystem
+    + getMeshRenderComponents() : List<Component>
+    + getName() : String
+    + getParent() : Entity
+    + getTransformComponent() : TransformComponent
+    + isEnabled() : boolean
+    + removeChild(child : Entity)
+    + removeComponent(component : Component)
+    + renderEntity()
+    + setEnabled(enabled : boolean)
+    + setGameSystem(gameSystem : GameSystem)
+    + setIsEnabled(isEnabled : boolean)
+    + setName(name : String)
+    + setParent(newParent : Entity)
+    + update(deltaTime : float)
+  }
+  class GameSystem {
+    - entities : List<Entity>
+    + GameSystem()
+    + addEntity(entity : Entity)
+    - calculateDistance(point1 : float[], point2 : float[]) : float
+    + getSystemMatrix(entity : Entity) : float[][]
+    + getSystemPosition(entity : Entity) : float[]
+    - multiplyMatrices(matrix1 : float[][], matrix2 : float[][]) : float[][]
+    + removeEntity(entity : Entity)
+    + renderSystem()
+    + sortEntitiesByDistance(referencePoint : float[])
+    + update(deltaTime : float)
+  }
+  class HealthComponent {
+    - currentHealth : float
+    - isAlive : boolean
+    - logger : Logger {static}
+    - maxHealth : float
+    + HealthComponent(maxHealth : float)
+    + applyDamage(damage : float)
+    + getCurrentHealth() : float
+    + getMaxHealth() : float
+    + heal(amount : float)
+    + isAlive() : boolean
+    + setAlive(isAlive : boolean)
+    + setCurrentHealth(currentHealth : float)
+    + setMaxHealth(maxHealth : float)
+    + update(deltaTime : float)
+  }
+  class TransformComponent {
+    - position : float[]
+    - rotation : float[]
+    - scale : float[]
+    + TransformComponent()
+    + TransformComponent(initPosition : float[], initRotation : float[], initScale : float[])
+    - applyRotation(matrix : float[][])
+    + getPosition() : float[]
+    + getRotation() : float[]
+    + getScale() : float[]
+    + getTransformMatrix() : float[][]
+    + setPosition(position : float[])
+    + setRotation(eulerAngles : float[])
+    + setScale(scale : float[])
+    + update(deltaTime : float)
+  }
+  class VelocityComponent {
+    - logger : Logger {static}
+    - velocityX : float
+    - velocityY : float
+    - velocityZ : float
+    + VelocityComponent(velocityX : float, velocityY : float, velocityZ : float)
+    + applyForce(forceX : float, forceY : float, forceZ : float)
+    + applyFriction(frictionCoefficient : float)
+    + getVelocityX() : float
+    + getVelocityY() : float
+    + getVelocityZ() : float
+    + setVelocityX(velocityX : float)
+    + setVelocityY(velocityY : float)
+    + setVelocityZ(velocityZ : float)
+    + update(deltaTime : float)
+  }
+}
+Entity -->  "-transform" TransformComponent
+Entity -->  "-parent" Entity
+Entity -->  "-children" Entity
+Entity -->  "-gameSystem" GameSystem
+Entity -->  "-components" Component
+HealthComponent --|> Component 
+TransformComponent --|> Component 
+VelocityComponent --|> Component 
+@enduml

entity-component-system/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+
+    The MIT License
+    Copyright © 2014-2022 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.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>java-design-patterns</artifactId>
+        <groupId>com.iluwatar</groupId>
+        <version>1.26.0-SNAPSHOT</version>
+    </parent>
+    <groupId>com.iluwatar</groupId>
+    <version>1.26.0-SNAPSHOT</version>
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>entity-component-system</artifactId>
+    <dependencies>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <configuration>
+                            <archive>
+                                <manifest>
+                                    <mainClass>com.iluwatar.entity-component-system.Main</mainClass>
+                                </manifest>
+                            </archive>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

entity-component-system/src/main/java/com/iluwatar/App.java

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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).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 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;
+
+/**
+ * The main entry point for the application.
+ * This class simulates a game loop where entities are created, updated, and their states are modified.
+ */
+public class App {
+
+  /**
+   * The main method that runs the application.
+   * It creates entities, adds components, updates them over several frames,
+   * and demonstrates applying damage and forces to entities.
+   *
+   * @param args Command-line arguments (not used in this application)
+   */
+  public static void main(String[] args) {
+
+
+    Entity entity1 = new Entity("Entity1");
+    Entity entity2 = new Entity("Entity2");
+
+    TransformComponent transform1 = new TransformComponent(new float[]{0.0f, 0.0f, 0.0f},
+        new float[]{0.0f, 0.0f, 0.0f}, new float[]{1.0f, 1.0f, 1.0f});
+    TransformComponent transform2 = new TransformComponent(new float[]{5.0f, 0.0f, 0.0f},
+        new float[]{0.0f, 45.0f, 0.0f}, new float[]{1.0f, 1.0f, 1.0f});
+
+    entity1.addComponent(transform1);
+    entity2.addComponent(transform2);
+
+    HealthComponent health1 = new HealthComponent(100);  // Ensure HealthComponent is implemented
+    entity1.addComponent(health1);
+
+    VelocityComponent velocity1 = new VelocityComponent(1.0f, 0.0f, 0.0f);
+    entity1.addComponent(velocity1);
+
+    GameSystem gameSystem = new GameSystem();
+    gameSystem.addEntity(entity1);
+    gameSystem.addEntity(entity2);
+
+    float deltaTime = 1.0f / 60.0f;
+
+    for (int i = 0; i < 10; i++) {
+
+      gameSystem.update(deltaTime);
+
+      if (i == 5) {
+        health1.applyDamage(30);
+      }
+
+      if (i == 3) {
+        velocity1.applyForce(0.5f, 0.0f, 0.0f);
+      }
+
+    }
+  }
+}

entity-component-system/src/main/java/com/iluwatar/Component.java

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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).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 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;
+
+/**
+ * Abstract class representing a component in the ECS system.
+ * Each component can be enabled or disabled and associated with an entity.
+ * Subclasses of this class must implement the update method.
+ */
+public abstract class Component {
+
+  private String name;
+  private boolean isEnabled;
+
+  /**
+   * Default constructor for the component.
+   * Initializes a new component with default values.
+   */
+  protected Component() {
+    // Constructor left empty intentionally, no specific initialization required
+  }
+
+  /**
+   * Gets the name of the component.
+   *
+   * @return the name of the component
+   */
+  public String getName() {
+    return name;
+  }
+
+  /**
+   * Sets the name of the component.
+   *
+   * @param name the name of the component
+   */
+  public void setName(String name) {
+    this.name = name;
+  }
+
+  /**
+   * Gets the enabled state of the component.
+   *
+   * @return true if the component is enabled, false otherwise
+   */
+  public boolean getEnabled() {
+    return isEnabled;
+  }
+
+  /**
+   * Sets the enabled state of the component.
+   *
+   * @param isEnabled true to enable the component, false to disable it
+   */
+  public void setEnabled(boolean isEnabled) {
+    this.isEnabled = isEnabled;
+  }
+
+  /**
+   * Abstract method to update the component.
+   * Subclasses must implement this method to define their update behavior.
+   *
+   * @param deltaTime the time elapsed since the last update
+   */
+  public abstract void update(float deltaTime);
+}