refactoring: execute around idiom (iluwatar#1945)

* Refactor execute around the idiom

* fix checkstyle errors

Co-authored-by: Subhrodip Mohanta <[email protected]>

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 
-> the user we let our service class open and close the file automatically, the user only has to 
+> A class needs to be provided for writing text strings to files. To make it easy for 
+> 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 {
-    try (var writer = new FileWriter(filename)) {
-      action.writeFile(writer);
+    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");
+        }
     }
-  }
 }
 ```
 
-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 -> {
-      writer.write("Hello");
-      writer.append(" ");
-      writer.append("there!");
-    };
-    new SimpleFileWriter("testfile.txt", writeHello);
+FileWriterAction writeHello = writer -> {
+    writer.write("Gandalf was here");
+};
+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 
-allocate/deallocate.
+* An API requires methods to be called in pairs such as open/close or allocate/deallocate.
 
 ## Credits
 

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

@@ -23,29 +23,39 @@
 
 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.
  *
  * <p>In this example, we have {@link SimpleFileWriter} class that opens and closes the file for
  * the user. The user specifies only what to do with the file by providing the {@link
  * FileWriterAction} implementation.
  */
+@Slf4j
 public class App {
 
   /**
    * Program entry point.
    */
   public static void main(String[] args) throws IOException {
 
+    // create the file writer and execute the custom action
     FileWriterAction writeHello = writer -> {
-      writer.write("Hello");
-      writer.append(" ");
-      writer.append("there!");
+      writer.write("Gandalf was here");
     };
     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 @@
 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");
     }
   }
 }