Added source code comments.

dependency-injection/src/main/java/com/iluwatar/AdvancedWizard.java

@@ -1,5 +1,12 @@
 package com.iluwatar;
 
+/**
+ * 
+ * AdvancedWizard implements inversion of control.
+ * It depends on abstraction that can be injected through
+ * its constructor.
+ *
+ */
 public class AdvancedWizard implements Wizard {
 	
 	private Tobacco tobacco;

dependency-injection/src/main/java/com/iluwatar/App.java

@@ -3,6 +3,27 @@ package com.iluwatar;
 import com.google.inject.Guice;
 import com.google.inject.Injector;
 
+/**
+ * 
+ * Dependency Injection pattern deals with how objects handle their dependencies. The pattern 
+ * implements so called inversion of control principle. Inversion of control has two specific rules:
+ *  - High-level modules should not depend on low-level modules. Both should depend on abstractions.
+ *  - Abstractions should not depend on details. Details should depend on abstractions.
+ *  
+ *  In this example we show you three different wizards. The first one (SimpleWizard) is a naive 
+ *  implementation violating the inversion of control principle. It depends directly on a concrete
+ *  implementation which cannot be changed.
+ *  
+ *  The second wizard (AdvancedWizard) is more flexible. It does not depend on any concrete implementation 
+ *  but abstraction. It utilizes Dependency Injection pattern allowing its Tobacco dependency to be
+ *  injected through its constructor. This way, handling the dependency is no longer the wizard's
+ *  responsibility. It is resolved outside the wizard class.
+ *  
+ *  The third example takes the pattern a step further. It uses Guice framework for Dependency Injection.
+ *  TobaccoModule binds a concrete implementation to abstraction. Injector is then used to create
+ *  GuiceWizard object with correct dependencies.
+ *
+ */
 public class App {
 	
     public static void main( String[] args ) {

dependency-injection/src/main/java/com/iluwatar/GuiceWizard.java

@@ -2,6 +2,13 @@ package com.iluwatar;
 
 import javax.inject.Inject;
 
+/**
+ * 
+ * GuiceWizard implements inversion of control.
+ * Its dependencies are injected through its constructor
+ * by Guice framework.
+ *
+ */
 public class GuiceWizard implements Wizard {
 	
 	private Tobacco tobacco;

dependency-injection/src/main/java/com/iluwatar/OldTobyTobacco.java

@@ -1,4 +1,9 @@
 package com.iluwatar;
 
+/**
+ * 
+ * OldTobyTobacco concrete Tobacco implementation
+ *
+ */
 public class OldTobyTobacco extends Tobacco {
 }

dependency-injection/src/main/java/com/iluwatar/RivendellTobacco.java

@@ -1,4 +1,9 @@
 package com.iluwatar;
 
+/**
+ * 
+ * RivendellTobacco concrete Tobacco implementation
+ *
+ */
 public class RivendellTobacco extends Tobacco {
 }

dependency-injection/src/main/java/com/iluwatar/SecondBreakfastTobacco.java

@@ -1,4 +1,9 @@
 package com.iluwatar;
 
+/**
+ * 
+ * SecondBreakfastTobacco concrete Tobacco implementation
+ *
+ */
 public class SecondBreakfastTobacco extends Tobacco {
 }

dependency-injection/src/main/java/com/iluwatar/SimpleWizard.java

@@ -1,5 +1,11 @@
 package com.iluwatar;
 
+/**
+ * 
+ * Naive Wizard implementation violating the inversion of control principle.
+ * It should depend on abstraction instead.
+ *
+ */
 public class SimpleWizard implements Wizard {
 	
 	private OldTobyTobacco tobacco = new OldTobyTobacco();

dependency-injection/src/main/java/com/iluwatar/Tobacco.java

@@ -1,5 +1,10 @@
 package com.iluwatar;
 
+/**
+ * 
+ * Tobacco abstraction
+ *
+ */
 public abstract class Tobacco {
 	
 	public void smoke(Wizard wizard) {

dependency-injection/src/main/java/com/iluwatar/TobaccoModule.java

@@ -2,6 +2,11 @@ package com.iluwatar;
 
 import com.google.inject.AbstractModule;
 
+/**
+ * 
+ * Guice module for binding certain concrete Tobacco implementation.
+ *
+ */
 public class TobaccoModule extends AbstractModule {
 
 	@Override

dependency-injection/src/main/java/com/iluwatar/Wizard.java

@@ -1,5 +1,10 @@
 package com.iluwatar;
 
+/**
+ * 
+ * Wizard interface
+ *
+ */
 public interface Wizard {
 	
 	void smoke();