checkstyle fixes - docs, indent etc

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

@@ -1,3 +1,6 @@
+/**
+ * Singleton pattern.
+ */
 package com.iluwatar.singleton;
 
 /**

singleton/src/main/java/com/iluwatar/singleton/EnumIvoryTower.java

@@ -1,10 +1,11 @@
+/**
+ * Enum Singleton class.
+ * Effective Java 2nd Edition (Joshua Bloch) p. 18
+ */
 package com.iluwatar.singleton;
 
 /**
- *
+ * Enum based singleton implementation.
- * Enum Singleton class.
- * Effective Java 2nd Edition (Joshua Bloch) p. 18
- *
  */
 public enum EnumIvoryTower {
 

singleton/src/main/java/com/iluwatar/singleton/InitializingOnDemandHolderIdiom.java

@@ -1,3 +1,6 @@
+/**
+ * Singleton pattern.
+ */
 package com.iluwatar.singleton;
 
 import java.io.Serializable;
@@ -7,30 +10,29 @@ import java.io.Serializable;
  * creating lazy initialized singleton object in Java.
  * refer to "The CERT Oracle Secure Coding Standard for Java"
  * By Dhruv Mohindra, Robert C. Seacord p.378
- * <p>
+ * <p/>
  * Singleton objects usually are heavy to create and sometimes need to serialize them.
  * This class also shows how to preserve singleton in serialized version of singleton.
  *
  * @author mortezaadi@gmail.com
- *
  */
-public class InitializingOnDemandHolderIdiom implements Serializable{
+public class InitializingOnDemandHolderIdiom implements Serializable {
 
     private static final long serialVersionUID = 1L;
 
-	private static class HelperHolder {
+    private InitializingOnDemandHolderIdiom() {
-		public static final InitializingOnDemandHolderIdiom INSTANCE = new InitializingOnDemandHolderIdiom();
     }
 
     public static InitializingOnDemandHolderIdiom getInstance() {
         return HelperHolder.INSTANCE;
     }
 
-	private InitializingOnDemandHolderIdiom() {
-	}
-
     protected Object readResolve() {
         return getInstance();
     }
 
+    private static class HelperHolder {
+        public static final InitializingOnDemandHolderIdiom INSTANCE = new InitializingOnDemandHolderIdiom();
+    }
+
 }

singleton/src/main/java/com/iluwatar/singleton/IvoryTower.java

@@ -1,19 +1,32 @@
+/**
+ * Singleton pattern.
+ */
 package com.iluwatar.singleton;
 
 /**
- * 
  * Singleton class.
  * Eagerly initialized static instance guarantees thread
  * safety.
- * 
  */
-public class IvoryTower {
+public final class IvoryTower {
 
+    /**
+     * Static to class instance of the class.
+     */
     private static IvoryTower instance = new IvoryTower();
 
+    /**
+     * Private constructor so nobody can instantiate the class.
+     */
     private IvoryTower() {
     }
 
+    /**
+     * To be called by user to
+     * obtain instance of the class.
+     *
+     * @return instance of the singleton.
+     */
     public static IvoryTower getInstance() {
         return instance;
     }

singleton/src/main/java/com/iluwatar/singleton/ThreadSafeDoubleCheckLocking.java

@@ -1,14 +1,17 @@
+/**
+ * Singleton pattern.
+ *
+ */
 package com.iluwatar.singleton;
 
 /**
  * Double check locking
- * <p>
+ * <p/>
  * http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html
- * <p>
+ * <p/>
  * Broken under Java 1.4.
  *
  * @author mortezaadi@gmail.com
- *
  */
 public class ThreadSafeDoubleCheckLocking {
 
@@ -16,11 +19,10 @@ public class ThreadSafeDoubleCheckLocking {
 
     /**
      * private constructor to prevent client from instantiating.
-	 * 
      */
     private ThreadSafeDoubleCheckLocking() {
         //to prevent instantiating by Reflection call
-		if(INSTANCE != null)
+        if (INSTANCE != null)
             throw new IllegalStateException("Already initialized.");
     }
 

singleton/src/main/java/com/iluwatar/singleton/ThreadSafeLazyLoadedIvoryTower.java

@@ -1,11 +1,12 @@
+/**
+ * Singleton pattern.
+ */
 package com.iluwatar.singleton;
 
 /**
- *
  * Thread-safe Singleton class.
  * The instance is lazily initialized and thus needs synchronization
  * mechanism.
- *
  */
 public class ThreadSafeLazyLoadedIvoryTower {