update multiton example

* Refactor execute around the idiom

* fix checkstyle errors

Co-authored-by: Subhrodip Mohanta <hello@subho.xyz>

execute-around/README.md

@@ -17,10 +17,10 @@ the user to specify only what to do with the resource.
 
 ## Explanation
 
-Real world example
+Real-world example
 
-> We need to provide a class that can be used to write text strings to files. To make it easy for 
+> A class needs to be provided for writing text strings to files. To make it easy for 
-> the user we let our service class open and close the file automatically, the user only has to 
+> the user, the service class opens and closes the file automatically. The user only has to 
 > specify what is written into which file.       
 
 In plain words
@@ -35,35 +35,50 @@ In plain words
 
 **Programmatic Example**
 
-Let's introduce our file writer class.
+`SimpleFileWriter` class implements the Execute Around idiom. It takes `FileWriterAction` as a
+constructor argument allowing the user to specify what gets written into the file.
 
 ```java
 @FunctionalInterface
 public interface FileWriterAction {
-
   void writeFile(FileWriter writer) throws IOException;
-
 }
 
+@Slf4j
 public class SimpleFileWriter {
-
+    public SimpleFileWriter(String filename, FileWriterAction action) throws IOException {
-  public SimpleFileWriter(String filename, FileWriterAction action) throws IOException {
+        LOGGER.info("Opening the file");
-    try (var writer = new FileWriter(filename)) {
+        try (var writer = new FileWriter(filename)) {
-      action.writeFile(writer);
+            LOGGER.info("Executing the action");
+            action.writeFile(writer);
+            LOGGER.info("Closing the file");
+        }
     }
-  }
 }
 ```
 
-To utilize the file writer the following code is needed.
+The following code demonstrates how `SimpleFileWriter` is used. `Scanner` is used to print the file
+contents after the writing finishes.
 
 ```java
-    FileWriterAction writeHello = writer -> {
+FileWriterAction writeHello = writer -> {
-      writer.write("Hello");
+    writer.write("Gandalf was here");
-      writer.append(" ");
+};
-      writer.append("there!");
+new SimpleFileWriter("testfile.txt", writeHello);
-    };
+
-    new SimpleFileWriter("testfile.txt", writeHello);
+var scanner = new Scanner(new File("testfile.txt"));
+while (scanner.hasNextLine()) {
+LOGGER.info(scanner.nextLine());
+}
+```
+
+Here's the console output.
+
+```
+21:18:07.185 [main] INFO com.iluwatar.execute.around.SimpleFileWriter - Opening the file
+21:18:07.188 [main] INFO com.iluwatar.execute.around.SimpleFileWriter - Executing the action
+21:18:07.189 [main] INFO com.iluwatar.execute.around.SimpleFileWriter - Closing the file
+21:18:07.199 [main] INFO com.iluwatar.execute.around.App - Gandalf was here
 ```
 
 ## Class diagram
@@ -74,8 +89,7 @@ To utilize the file writer the following code is needed.
 
 Use the Execute Around idiom when
 
-* You use an API that requires methods to be called in pairs such as open/close or 
+* An API requires methods to be called in pairs such as open/close or allocate/deallocate.
-allocate/deallocate.
 
 ## Credits
 

execute-around/src/main/java/com/iluwatar/execute/around/App.java

@@ -23,10 +23,14 @@
 
 package com.iluwatar.execute.around;
 
+import java.io.File;
 import java.io.IOException;
+import java.util.Scanner;
+
+import lombok.extern.slf4j.Slf4j;
 
 /**
- * The Execute Around idiom specifies some code to be executed before and after a method. Typically
+ * The Execute Around idiom specifies executable code before and after a method. Typically
  * the idiom is used when the API has methods to be executed in pairs, such as resource
  * allocation/deallocation or lock acquisition/release.
  *
@@ -34,6 +38,7 @@ import java.io.IOException;
  * the user. The user specifies only what to do with the file by providing the {@link
  * FileWriterAction} implementation.
  */
+@Slf4j
 public class App {
 
   /**
@@ -41,11 +46,16 @@ public class App {
    */
   public static void main(String[] args) throws IOException {
 
+    // create the file writer and execute the custom action
     FileWriterAction writeHello = writer -> {
-      writer.write("Hello");
+      writer.write("Gandalf was here");
-      writer.append(" ");
-      writer.append("there!");
     };
     new SimpleFileWriter("testfile.txt", writeHello);
+
+    // print the file contents
+    var scanner = new Scanner(new File("testfile.txt"));
+    while (scanner.hasNextLine()) {
+      LOGGER.info(scanner.nextLine());
+    }
   }
 }

execute-around/src/main/java/com/iluwatar/execute/around/SimpleFileWriter.java

@@ -26,18 +26,24 @@ package com.iluwatar.execute.around;
 import java.io.FileWriter;
 import java.io.IOException;
 
+import lombok.extern.slf4j.Slf4j;
+
 /**
  * SimpleFileWriter handles opening and closing file for the user. The user only has to specify what
  * to do with the file resource through {@link FileWriterAction} parameter.
  */
+@Slf4j
 public class SimpleFileWriter {
 
   /**
    * Constructor.
    */
   public SimpleFileWriter(String filename, FileWriterAction action) throws IOException {
+    LOGGER.info("Opening the file");
     try (var writer = new FileWriter(filename)) {
+      LOGGER.info("Executing the action");
       action.writeFile(writer);
+      LOGGER.info("Closing the file");
     }
   }
 }

multiton/README.md

@@ -15,18 +15,18 @@ Registry
 
 ## Intent
 
-Ensure a class only has limited number of instances and provide a global point of access to them.
+Ensure a class only has a limited number of instances and provide a global point of access to them.
 
 ## Explanation
 
-Real world example
+Real-world example
 
 > The Nazgûl, also called ringwraiths or the Nine Riders, are Sauron's most terrible servants. By 
-> definition there's always nine of them.           
+> definition, there's always nine of them.           
 
 In plain words
 
-> Multiton pattern ensures there's predefined amount of instances available globally.   
+> Multiton pattern ensures there are a predefined amount of instances available globally.   
 
 Wikipedia says
 
@@ -81,29 +81,54 @@ public final class Nazgul {
 And here's how we access the `Nazgul` instances.
 
 ```java
-    LOGGER.info("KHAMUL={}", Nazgul.getInstance(NazgulName.KHAMUL));
+// eagerly initialized multiton
-    LOGGER.info("MURAZOR={}", Nazgul.getInstance(NazgulName.MURAZOR));
+LOGGER.info("Printing out eagerly initialized multiton contents");
-    LOGGER.info("DWAR={}", Nazgul.getInstance(NazgulName.DWAR));
+LOGGER.info("KHAMUL={}", Nazgul.getInstance(NazgulName.KHAMUL));
-    LOGGER.info("JI_INDUR={}", Nazgul.getInstance(NazgulName.JI_INDUR));
+LOGGER.info("MURAZOR={}", Nazgul.getInstance(NazgulName.MURAZOR));
-    LOGGER.info("AKHORAHIL={}", Nazgul.getInstance(NazgulName.AKHORAHIL));
+LOGGER.info("DWAR={}", Nazgul.getInstance(NazgulName.DWAR));
-    LOGGER.info("HOARMURATH={}", Nazgul.getInstance(NazgulName.HOARMURATH));
+LOGGER.info("JI_INDUR={}", Nazgul.getInstance(NazgulName.JI_INDUR));
-    LOGGER.info("ADUNAPHEL={}", Nazgul.getInstance(NazgulName.ADUNAPHEL));
+LOGGER.info("AKHORAHIL={}", Nazgul.getInstance(NazgulName.AKHORAHIL));
-    LOGGER.info("REN={}", Nazgul.getInstance(NazgulName.REN));
+LOGGER.info("HOARMURATH={}", Nazgul.getInstance(NazgulName.HOARMURATH));
-    LOGGER.info("UVATHA={}", Nazgul.getInstance(NazgulName.UVATHA));
+LOGGER.info("ADUNAPHEL={}", Nazgul.getInstance(NazgulName.ADUNAPHEL));
+LOGGER.info("REN={}", Nazgul.getInstance(NazgulName.REN));
+LOGGER.info("UVATHA={}", Nazgul.getInstance(NazgulName.UVATHA));
+
+// enum multiton
+LOGGER.info("Printing out enum-based multiton contents");
+LOGGER.info("KHAMUL={}", NazgulEnum.KHAMUL);
+LOGGER.info("MURAZOR={}", NazgulEnum.MURAZOR);
+LOGGER.info("DWAR={}", NazgulEnum.DWAR);
+LOGGER.info("JI_INDUR={}", NazgulEnum.JI_INDUR);
+LOGGER.info("AKHORAHIL={}", NazgulEnum.AKHORAHIL);
+LOGGER.info("HOARMURATH={}", NazgulEnum.HOARMURATH);
+LOGGER.info("ADUNAPHEL={}", NazgulEnum.ADUNAPHEL);
+LOGGER.info("REN={}", NazgulEnum.REN);
+LOGGER.info("UVATHA={}", NazgulEnum.UVATHA);
 ```
 
 Program output:
 
 ```
-KHAMUL=com.iluwatar.multiton.Nazgul@2b214b94
+20:35:07.413 [main] INFO com.iluwatar.multiton.App - Printing out eagerly initialized multiton contents
-MURAZOR=com.iluwatar.multiton.Nazgul@17814b1c
+20:35:07.417 [main] INFO com.iluwatar.multiton.App - KHAMUL=com.iluwatar.multiton.Nazgul@48cf768c
-DWAR=com.iluwatar.multiton.Nazgul@7ac9af2a
+20:35:07.419 [main] INFO com.iluwatar.multiton.App - MURAZOR=com.iluwatar.multiton.Nazgul@7960847b
-JI_INDUR=com.iluwatar.multiton.Nazgul@7bb004b8
+20:35:07.419 [main] INFO com.iluwatar.multiton.App - DWAR=com.iluwatar.multiton.Nazgul@6a6824be
-AKHORAHIL=com.iluwatar.multiton.Nazgul@78e89bfe
+20:35:07.419 [main] INFO com.iluwatar.multiton.App - JI_INDUR=com.iluwatar.multiton.Nazgul@5c8da962
-HOARMURATH=com.iluwatar.multiton.Nazgul@652ce654
+20:35:07.419 [main] INFO com.iluwatar.multiton.App - AKHORAHIL=com.iluwatar.multiton.Nazgul@512ddf17
-ADUNAPHEL=com.iluwatar.multiton.Nazgul@522ba524
+20:35:07.419 [main] INFO com.iluwatar.multiton.App - HOARMURATH=com.iluwatar.multiton.Nazgul@2c13da15
-REN=com.iluwatar.multiton.Nazgul@29c5ee1d
+20:35:07.419 [main] INFO com.iluwatar.multiton.App - ADUNAPHEL=com.iluwatar.multiton.Nazgul@77556fd
-UVATHA=com.iluwatar.multiton.Nazgul@15cea7b0
+20:35:07.419 [main] INFO com.iluwatar.multiton.App - REN=com.iluwatar.multiton.Nazgul@368239c8
+20:35:07.420 [main] INFO com.iluwatar.multiton.App - UVATHA=com.iluwatar.multiton.Nazgul@9e89d68
+20:35:07.420 [main] INFO com.iluwatar.multiton.App - Printing out enum-based multiton contents
+20:35:07.420 [main] INFO com.iluwatar.multiton.App - KHAMUL=KHAMUL
+20:35:07.420 [main] INFO com.iluwatar.multiton.App - MURAZOR=MURAZOR
+20:35:07.420 [main] INFO com.iluwatar.multiton.App - DWAR=DWAR
+20:35:07.420 [main] INFO com.iluwatar.multiton.App - JI_INDUR=JI_INDUR
+20:35:07.421 [main] INFO com.iluwatar.multiton.App - AKHORAHIL=AKHORAHIL
+20:35:07.421 [main] INFO com.iluwatar.multiton.App - HOARMURATH=HOARMURATH
+20:35:07.421 [main] INFO com.iluwatar.multiton.App - ADUNAPHEL=ADUNAPHEL
+20:35:07.421 [main] INFO com.iluwatar.multiton.App - REN=REN
+20:35:07.421 [main] INFO com.iluwatar.multiton.App - UVATHA=UVATHA
 ```
 
 ## Class diagram
@@ -114,5 +139,5 @@ UVATHA=com.iluwatar.multiton.Nazgul@15cea7b0
 
 Use the Multiton pattern when
 
-* There must be specific number of instances of a class, and they must be accessible to clients from 
+* There must be a specific number of instances of a class, and they must be accessible to clients from 
 a well-known access point.

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

@@ -26,13 +26,13 @@ package com.iluwatar.multiton;
 import lombok.extern.slf4j.Slf4j;
 
 /**
- * Whereas Singleton design pattern introduces single globally accessible object the Multiton
+ * Whereas Singleton design pattern introduces single globally accessible object, the Multiton
  * pattern defines many globally accessible objects. The client asks for the correct instance from
- * the Multiton by passing an enumeration as parameter.
+ * the Multiton by passing an enumeration as a parameter.
  *
  * <p>There is more than one way to implement the multiton design pattern. In the first example
  * {@link Nazgul} is the Multiton and we can ask single {@link Nazgul} from it using {@link
- * NazgulName}. The {@link Nazgul}s are statically initialized and stored in concurrent hash map.
+ * NazgulName}. The {@link Nazgul}s are statically initialized and stored in a concurrent hash map.
  *
  * <p>In the enum implementation {@link NazgulEnum} is the multiton. It is static and mutable
  * because of the way java supports enums.
@@ -47,6 +47,7 @@ public class App {
    */
   public static void main(String[] args) {
     // eagerly initialized multiton
+    LOGGER.info("Printing out eagerly initialized multiton contents");
     LOGGER.info("KHAMUL={}", Nazgul.getInstance(NazgulName.KHAMUL));
     LOGGER.info("MURAZOR={}", Nazgul.getInstance(NazgulName.MURAZOR));
     LOGGER.info("DWAR={}", Nazgul.getInstance(NazgulName.DWAR));
@@ -58,6 +59,7 @@ public class App {
     LOGGER.info("UVATHA={}", Nazgul.getInstance(NazgulName.UVATHA));
 
     // enum multiton
+    LOGGER.info("Printing out enum-based multiton contents");
     LOGGER.info("KHAMUL={}", NazgulEnum.KHAMUL);
     LOGGER.info("MURAZOR={}", NazgulEnum.MURAZOR);
     LOGGER.info("DWAR={}", NazgulEnum.DWAR);

multiton/src/test/java/com/iluwatar/multiton/NazgulTest.java

@@ -48,5 +48,4 @@ public class NazgulTest {
       assertEquals(name, nazgul.getName());
     }
   }
-
 }