Added second MVC example. This time the view is registered as observer to the model and gets update notifications that way.

model-view-controller/src/main/java/com/iluwatar/model/view/controller/with/observer/App.java

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+package com.iluwatar.model.view.controller.with.observer;
+
+/**
+ * 
+ * In this second example the model-view relationship is different. This time we use the Observer pattern to notify
+ * the {@link GiantView} each time the {@link GiantModel} is changed. This way the {@link GiantController} responsibilities
+ * are narrowed and it only needs to modify the {@link GiantModel} according to the user input.
+ * 
+ */
+public class App {
+	
+	/**
+	 * Program entry point
+	 * @param args command line args
+	 */
+    public static void main( String[] args ) {
+    	// create model, view and controller
+    	GiantModel giant = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
+    	GiantView view = new GiantView();
+    	GiantController controller = new GiantController(giant, view);
+    	// initial display
+    	controller.updateView();
+    	// controller receives some interactions that affect the giant
+    	// model modifications trigger the view rendering automatically
+    	controller.setHealth(Health.WOUNDED);
+    	controller.setNourishment(Nourishment.HUNGRY);
+    	controller.setFatigue(Fatigue.TIRED);
+    }
+}

model-view-controller/src/main/java/com/iluwatar/model/view/controller/with/observer/Fatigue.java

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+package com.iluwatar.model.view.controller.with.observer;
+
+/**
+ * 
+ * Fatigue enumeration
+ *
+ */
+public enum Fatigue {
+
+	ALERT("alert"), TIRED("tired"), SLEEPING("sleeping");
+	
+	private String title;
+	
+	Fatigue(String title) {
+		this.title = title;
+	}
+
+	@Override
+	public String toString() {
+		return title;
+	}	
+}

model-view-controller/src/main/java/com/iluwatar/model/view/controller/with/observer/GiantController.java

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+package com.iluwatar.model.view.controller.with.observer;
+
+/**
+ * 
+ * GiantController updates the giant model.
+ *
+ */
+public class GiantController {
+
+	private GiantModel giant;
+	private GiantView view;
+
+	public GiantController(GiantModel giant, GiantView view) {
+		this.giant = giant;
+		this.view = view;
+		this.giant.registerObserver(this.view);
+	}
+	
+	public Health getHealth() {
+		return giant.getHealth();
+	}
+
+	public void setHealth(Health health) {
+		this.giant.setHealth(health);
+	}
+
+	public Fatigue getFatigue() {
+		return giant.getFatigue();
+	}
+
+	public void setFatigue(Fatigue fatigue) {
+		this.giant.setFatigue(fatigue);
+	}
+
+	public Nourishment getNourishment() {
+		return giant.getNourishment();
+	}
+
+	public void setNourishment(Nourishment nourishment) {
+		this.giant.setNourishment(nourishment);
+	}
+	
+	public void updateView() {
+		this.view.displayGiant(giant);
+	}
+}

model-view-controller/src/main/java/com/iluwatar/model/view/controller/with/observer/GiantModel.java

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+package com.iluwatar.model.view.controller.with.observer;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 
+ * GiantModel contains the giant data.
+ *
+ */
+public class GiantModel {
+	
+	private Health health;
+	private Fatigue fatigue;
+	private Nourishment nourishment;
+	private List<GiantModelObserver> observers = new ArrayList<>();
+
+	GiantModel(Health health, Fatigue fatigue, Nourishment nourishment) {
+		this.health = health;
+		this.fatigue = fatigue;
+		this.nourishment = nourishment;	
+	}
+
+	public Health getHealth() {
+		return health;
+	}
+
+	public void setHealth(Health health) {
+		this.health = health;
+		notifyObservers();
+	}
+
+	public Fatigue getFatigue() {
+		return fatigue;
+	}
+
+	public void setFatigue(Fatigue fatigue) {
+		this.fatigue = fatigue;
+		notifyObservers();
+	}
+
+	public Nourishment getNourishment() {
+		return nourishment;
+	}
+
+	public void setNourishment(Nourishment nourishment) {
+		this.nourishment = nourishment;
+		notifyObservers();
+	}
+	
+	@Override
+	public String toString() {
+		return String.format("The giant looks %s, %s and %s.", health, fatigue, nourishment);
+	}
+	
+	public void registerObserver(GiantModelObserver observer) {
+		observers.add(observer);
+	}
+	
+	private void notifyObservers() {
+		observers.stream().forEach((GiantModelObserver o) -> o.modelChanged(this));
+	}
+}

model-view-controller/src/main/java/com/iluwatar/model/view/controller/with/observer/GiantModelObserver.java

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+package com.iluwatar.model.view.controller.with.observer;
+
+/**
+ * 
+ * GiantModelObserver is the interface for delivering update notifications.
+ *
+ */
+public interface GiantModelObserver {
+	
+	void modelChanged(GiantModel model);
+
+}

model-view-controller/src/main/java/com/iluwatar/model/view/controller/with/observer/GiantView.java

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+package com.iluwatar.model.view.controller.with.observer;
+
+/**
+ * 
+ * GiantView displays the giant
+ *
+ */
+public class GiantView implements GiantModelObserver {
+
+	public void displayGiant(GiantModel giant) {
+		System.out.println(giant);
+	}
+
+	@Override
+	public void modelChanged(GiantModel model) {
+		displayGiant(model);
+	}
+}

model-view-controller/src/main/java/com/iluwatar/model/view/controller/with/observer/Health.java

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+package com.iluwatar.model.view.controller.with.observer;
+
+/**
+ * 
+ * Health enumeration
+ *
+ */
+public enum Health {
+	
+	HEALTHY("healthy"), WOUNDED("wounded"), DEAD("dead");
+	
+	private String title;
+	
+	Health(String title) {
+		this.title = title;
+	}
+
+	@Override
+	public String toString() {
+		return title;
+	}
+}

model-view-controller/src/main/java/com/iluwatar/model/view/controller/with/observer/Nourishment.java

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+package com.iluwatar.model.view.controller.with.observer;
+
+/**
+ * 
+ * Nourishment enumeration
+ *
+ */
+public enum Nourishment {
+
+	SATURATED("saturated"), HUNGRY("hungry"), STARVING("starving");
+	
+	private String title;
+	
+	Nourishment(String title) {
+		this.title = title;
+	}
+
+	@Override
+	public String toString() {
+		return title;
+	}	
+}

model-view-controller/src/test/java/com/iluwatar/model/view/controller/with/observer/AppTest.java

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+package com.iluwatar.model.view.controller.with.observer;
+
+import org.junit.Test;
+
+import com.iluwatar.model.view.controller.with.observer.App;
+
+/**
+ * 
+ * Application test
+ *
+ */
+public class AppTest {
+	
+	@Test
+	public void test() {
+		String[] args = {};
+		App.main(args);
+	}
+}