Update singleton

singleton/README.md

@@ -13,13 +13,12 @@ tags:
 
 Ensure a class only has one instance, and provide a global point of access to it.
 
-
 ## Explanation
 
-Real world example
+Real-world example
 
 > There can only be one ivory tower where the wizards study their magic. The same enchanted ivory 
-> tower is always used by the wizards. Ivory tower here is singleton.
+> tower is always used by the wizards. The ivory tower here is a singleton.
 
 In plain words
 
@@ -48,7 +47,15 @@ Then in order to use:
 ```java
     var enumIvoryTower1 = EnumIvoryTower.INSTANCE;
     var enumIvoryTower2 = EnumIvoryTower.INSTANCE;
-assertEquals(enumIvoryTower1, enumIvoryTower2); // true
+    LOGGER.info("enumIvoryTower1={}", enumIvoryTower1);
+    LOGGER.info("enumIvoryTower2={}", enumIvoryTower2);
+```
+
+The console output
+
+```
+enumIvoryTower1=com.iluwatar.singleton.EnumIvoryTower@1221555852
+enumIvoryTower2=com.iluwatar.singleton.EnumIvoryTower@1221555852
 ```
 
 ## Class diagram
@@ -62,13 +69,13 @@ Use the Singleton pattern when
 * There must be exactly one instance of a class, and it must be accessible to clients from a well-known access point
 * When the sole instance should be extensible by subclassing, and clients should be able to use an extended instance without modifying their code
 
-## Typical Use Case
+Some typical use cases for the Singleton
 
 * The logging class
 * Managing a connection to a database
 * File manager
 
-## Real world examples
+## Known uses
 
 * [java.lang.Runtime#getRuntime()](http://docs.oracle.com/javase/8/docs/api/java/lang/Runtime.html#getRuntime%28%29)
 * [java.awt.Desktop#getDesktop()](http://docs.oracle.com/javase/8/docs/api/java/awt/Desktop.html#getDesktop--)
@@ -77,8 +84,8 @@ Use the Singleton pattern when
 
 ## Consequences
 
-* Violates Single Responsibility Principle (SRP) by controlling their own creation and lifecycle.
+* Violates Single Responsibility Principle (SRP) by controlling their creation and lifecycle.
-* Encourages using a global shared instance which prevents an object and resources used by this object from being deallocated.     
+* Encourages using a globally shared instance which prevents an object and resources used by this object from being deallocated.     
 * Creates tightly coupled code. The clients of the Singleton become difficult to test.
 * Makes it almost impossible to subclass a Singleton.
 

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

@@ -30,20 +30,20 @@ import lombok.extern.slf4j.Slf4j;
  * classloader instance and provides global access to it.</p>
  *
  * <p>One of the risks of this pattern is that bugs resulting from setting a singleton up in a
- * distributed environment can be tricky to debug, since it will work fine if you debug with a
+ * distributed environment can be tricky to debug since it will work fine if you debug with a
  * single classloader. Additionally, these problems can crop up a while after the implementation of
- * a singleton, since they may start out synchronous and only become async with time, so it may
+ * a singleton, since they may start synchronous and only become async with time, so it may
- * not be clear why you are seeing certain changes in behaviour.</p>
+ * not be clear why you are seeing certain changes in behavior.</p>
  *
  * <p>There are many ways to implement the Singleton. The first one is the eagerly initialized
  * instance in {@link IvoryTower}. Eager initialization implies that the implementation is thread
- * safe. If you can afford giving up control of the instantiation moment, then this implementation
+ * safe. If you can afford to give up control of the instantiation moment, then this implementation
  * will suit you fine.</p>
  *
- * <p>The other option to implement eagerly initialized Singleton is enum based Singleton. The
+ * <p>The other option to implement eagerly initialized Singleton is enum-based Singleton. The
- * example is found in {@link EnumIvoryTower}. At first glance the code looks short and simple.
+ * example is found in {@link EnumIvoryTower}. At first glance, the code looks short and simple.
  * However, you should be aware of the downsides including committing to implementation strategy,
- * extending the enum class, serializability and restrictions to coding. These are extensively
+ * extending the enum class, serializability, and restrictions to coding. These are extensively
  * discussed in Stack Overflow: http://programmers.stackexchange.com/questions/179386/what-are-the-downsides-of-implementing
  * -a-singleton-with-javas-enum</p>
  *
@@ -56,7 +56,7 @@ import lombok.extern.slf4j.Slf4j;
  * ThreadSafeLazyLoadedIvoryTower} since it doesn't synchronize the whole access method but only the
  * method internals on specific conditions.</p>
  *
- * <p>Yet another way to implement thread safe lazily initialized Singleton can be found in
+ * <p>Yet another way to implement thread-safe lazily initialized Singleton can be found in
  * {@link InitializingOnDemandHolderIdiom}. However, this implementation requires at least Java 8
  * API level to work.</p>
  */