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iluwatariluwatar
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added observer sample
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8 files changed

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8 files changed

+163
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‎observer/pom.xml‎

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<?xml version="1.0"?>
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<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>com.iluwatar</groupId>
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<artifactId>java-design-patterns</artifactId>
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<version>1.0-SNAPSHOT</version>
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</parent>
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<groupId>com.iluwatar</groupId>
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<artifactId>observer</artifactId>
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<version>1.0-SNAPSHOT</version>
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<name>observer</name>
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<url>http://maven.apache.org</url>
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<dependencies>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>3.8.1</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎observer/src/main/java/com/iluwatar/App.java‎

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package com.iluwatar;
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public class App
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{
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public static void main( String[] args )
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{
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Weather weather = new Weather();
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weather.addObserver(new Orcs());
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weather.addObserver(new Hobbits());
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weather.timePasses();
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weather.timePasses();
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weather.timePasses();
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weather.timePasses();
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}
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}

‎observer/src/main/java/com/iluwatar/Hobbits.java‎

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package com.iluwatar;
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public class Hobbits implements WeatherObserver {
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@Override
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public void update(WeatherType currentWeather) {
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switch (currentWeather) {
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case COLD:
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System.out.println("The hobbits are shivering in the cold weather.");
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break;
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case RAINY:
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System.out.println("The hobbits look for cover from the rain.");
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break;
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case SUNNY:
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System.out.println("The happy hobbits bade in the warm sun.");
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break;
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case WINDY:
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System.out.println("The hobbits hold their hats tightly in the windy weather.");
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break;
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default:
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break;
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}
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}
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}

‎observer/src/main/java/com/iluwatar/Orcs.java‎

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package com.iluwatar;
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public class Orcs implements WeatherObserver {
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@Override
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public void update(WeatherType currentWeather) {
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switch (currentWeather) {
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case COLD:
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System.out.println("The orcs are freezing cold.");
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break;
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case RAINY:
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System.out.println("The orcs are dripping wet.");
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break;
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case SUNNY:
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System.out.println("The sun hurts the orcs' eyes.");
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break;
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case WINDY:
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System.out.println("The orc smell almost vanishes in the wind.");
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break;
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default:
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break;
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}
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}
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}

‎observer/src/main/java/com/iluwatar/Weather.java‎

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package com.iluwatar;
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import java.util.ArrayList;
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import java.util.List;
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public class Weather {
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private WeatherType currentWeather;
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private List<WeatherObserver> observers;
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public Weather() {
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observers = new ArrayList<>();
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currentWeather = WeatherType.SUNNY;
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}
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public void addObserver(WeatherObserver obs) {
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observers.add(obs);
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}
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public void removeObserver(WeatherObserver obs) {
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observers.remove(obs);
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}
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public void timePasses() {
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switch (currentWeather) {
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case COLD:
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currentWeather = WeatherType.SUNNY;
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break;
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case RAINY:
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currentWeather = WeatherType.WINDY;
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break;
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case SUNNY:
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currentWeather = WeatherType.RAINY;
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break;
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case WINDY:
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currentWeather = WeatherType.COLD;
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break;
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default:
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break;
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}
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System.out.println("The weather now changes to " + currentWeather);
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notifyObservers();
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}
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private void notifyObservers() {
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for (WeatherObserver obs: observers) {
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obs.update(currentWeather);
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}
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}
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}

‎observer/src/main/java/com/iluwatar/WeatherObserver.java‎

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package com.iluwatar;
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public interface WeatherObserver {
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void update(WeatherType currentWeather);
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}

‎observer/src/main/java/com/iluwatar/WeatherType.java‎

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package com.iluwatar;
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public enum WeatherType {
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SUNNY,
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RAINY,
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WINDY,
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COLD;
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public String toString() {
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return this.name().toLowerCase();
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};
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}

‎pom.xml‎

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<module>iterator</module>
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<module>mediator</module>
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<module>memento</module>
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<module>observer</module>
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</modules>
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<build>

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