eliminate all warnings of checkstyle.

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

@@ -1,26 +1,29 @@
 /**
  * Singleton pattern.
  */
+
 package com.iluwatar.singleton;
 
 /**
- *
  * Singleton pattern ensures that the class ({@link IvoryTower}) can have only one
  * existing instance per Java classloader instance and provides global access to it.
- * <p>
+ * <p/>
  * http://stackoverflow.com/questions/70689/what-is-an-efficient-way-to-implement-a-singleton-pattern-in-java
- *<p>
+ * <p/>
- * The risk of this pattern is that bugs resulting from setting a singleton up in a distributed environment can 
+ * The risk of this pattern is that bugs resulting from setting a singleton up in
- * be tricky to debug, since it will work fine if you debug with a single classloader. Additionally, these
+ * a distributed environment can be tricky to debug, since it will work fine if you
- * problems can crop up a while after the implementation of a singleton, since they may start out synchronous and
+ * debug with a single classloader. Additionally, these problems can crop up a while
- * only become async with time, so you it may not be clear why you are seeing certain changes in behaviour.
+ * after the implementation of a singleton, since they may start out synchronous and
- * <p>
+ * only become async with time, so you it may not be clear why you are seeing certain
+ * changes in behaviour.
+ * <p/>
  * http://stackoverflow.com/questions/17721263/singleton-across-jvm-or-application-instance-or-tomcat-instance
  */
 public class App {
 
   /**
-     * Program entry point
+   * Program entry point.
+   *
    * @param args command line args
    */
   public static void main(String[] args) {
@@ -45,9 +48,11 @@ public class App {
     System.out.println("enumIvoryTower1=" + enumIvoryTower1);
     System.out.println("enumIvoryTower2=" + enumIvoryTower2);
 
-        InitializingOnDemandHolderIdiom demandHolderIdiom = InitializingOnDemandHolderIdiom.getInstance();
+    InitializingOnDemandHolderIdiom demandHolderIdiom =
+            InitializingOnDemandHolderIdiom.getInstance();
     System.out.println(demandHolderIdiom);
-        InitializingOnDemandHolderIdiom demandHolderIdiom2 = InitializingOnDemandHolderIdiom.getInstance();
+    InitializingOnDemandHolderIdiom demandHolderIdiom2 =
+            InitializingOnDemandHolderIdiom.getInstance();
     System.out.println(demandHolderIdiom2);
 
     ThreadSafeDoubleCheckLocking dcl1 = ThreadSafeDoubleCheckLocking.getInstance();

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

@@ -1,11 +1,8 @@
-/**
- * Enum Singleton class.
- * Effective Java 2nd Edition (Joshua Bloch) p. 18
- */
 package com.iluwatar.singleton;
 
 /**
  * Enum based singleton implementation.
+ * Effective Java 2nd Edition (Joshua Bloch) p. 18
  */
 public enum EnumIvoryTower {
 

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

@@ -1,6 +1,3 @@
-/**
- * Singleton pattern.
- */
 package com.iluwatar.singleton;
 
 import java.io.Serializable;
@@ -32,7 +29,8 @@ public class InitializingOnDemandHolderIdiom implements Serializable {
   }
 
   private static class HelperHolder {
-        public static final InitializingOnDemandHolderIdiom INSTANCE = new InitializingOnDemandHolderIdiom();
+    public static final InitializingOnDemandHolderIdiom INSTANCE =
+            new InitializingOnDemandHolderIdiom();
   }
 
 }

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

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

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

@@ -1,7 +1,3 @@
-/**
- * Singleton pattern.
- *
- */
 package com.iluwatar.singleton;
 
 /**
@@ -22,10 +18,16 @@ public class ThreadSafeDoubleCheckLocking {
    */
   private ThreadSafeDoubleCheckLocking() {
     //to prevent instantiating by Reflection call
-        if (INSTANCE != null)
+    if (INSTANCE != null) {
       throw new IllegalStateException("Already initialized.");
     }
+  }
 
+  /**
+   * Public accessor.
+   *
+   * @return an instance of the class.
+   */
   public static ThreadSafeDoubleCheckLocking getInstance() {
     //local variable increases performance by 25 percent
     //Joshua Bloch "Effective Java, Second Edition", p. 283-284

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

@@ -1,6 +1,3 @@
-/**
- * Singleton pattern.
- */
 package com.iluwatar.singleton;
 
 /**
@@ -15,11 +12,12 @@ public class ThreadSafeLazyLoadedIvoryTower {
   private ThreadSafeLazyLoadedIvoryTower() {
   }
 
-    public synchronized static ThreadSafeLazyLoadedIvoryTower getInstance() {
+  /**
-        /*
    * The instance gets created only when it is called for first time.
    * Lazy-loading
    */
+  public synchronized static ThreadSafeLazyLoadedIvoryTower getInstance() {
+
     if (instance == null) {
       instance = new ThreadSafeLazyLoadedIvoryTower();
     }