#107 Improve JavaDoc for Null Object example

null-object/src/main/java/com/iluwatar/nullobject/App.java

@@ -5,7 +5,7 @@ package com.iluwatar.nullobject;
  * Null Object pattern replaces null values with neutral objects.
  * Many times this simplifies algorithms since no extra null checks
  * are needed.
- * 
+ * <p>
  * In this example we build a binary tree where the nodes are either
  * normal or Null Objects. No null values are used in the tree making
  * the traversal easy.
@@ -13,6 +13,10 @@ package com.iluwatar.nullobject;
  */
 public class App 
 {
+	/**
+	 * Program entry point
+	 * @param args command line args
+	 */
     public static void main( String[] args ) {
     	
     	Node root = new NodeImpl("1",

null-object/src/main/java/com/iluwatar/nullobject/NullNode.java

@@ -3,7 +3,7 @@ package com.iluwatar.nullobject;
 /**
  * 
  * Null Object implementation for binary tree node.
- * 
+ * <p>
  * Implemented as Singleton, since all the NullNodes are the same.
  *
  */

null-object/src/test/java/com/iluwatar/nullobject/AppTest.java

@@ -4,6 +4,11 @@ import org.junit.Test;
 
 import com.iluwatar.nullobject.App;
 
+/**
+ * 
+ * Application test
+ *
+ */
 public class AppTest {
 
 	@Test