fix: update formatting for consistency, add examples of missing message format

Author: Bonajo

content/docs/week08.adoc

@@ -2,7 +2,7 @@
 title: "08 I18N, exceptions and logging"
 description: ""
 date: 2025-04-24T10:31:29+02:00
-draft: true
+draft: false
 images: []
 slug: "internationalisation"
 menu: 

topics/code/exex/src/exex/CircleWithException.java

@@ -16,15 +16,15 @@ public class CircleWithException {
      * Construct a circle with radius 1
      */
     public CircleWithException() {
-        this( 1.0 );
+        this(1.0);
     }
 
     /**
      * Construct a circle with a specified radius
      */
-    public CircleWithException( double newRadius ) {
-        setRadius( newRadius );
-        numberOfObjects ++;
+    public CircleWithException(double newRadius) {
+        setRadius(newRadius);
+        numberOfObjects++;
     }
 
     /**
@@ -37,13 +37,13 @@ public double getRadius() {
     /**
      * Set a new radius
      */
-    public void setRadius( double newRadius )
+    public void setRadius(double newRadius)
             throws IllegalArgumentException {
-        if ( newRadius >= 0 ) {
+        if (newRadius >= 0) {
             radius = newRadius;
         } else {
             throw new IllegalArgumentException(
-                    "Radius cannot be negative" );
+                    "Radius cannot be negative");
         }
     }
 

topics/code/exex/src/exex/QuotientWithException.java

@@ -4,31 +4,31 @@
 
 public class QuotientWithException {
 
-    public static int quotient( int number1, int number2 ) {
-        if ( number2 == 0 ) {
-            throw new ArithmeticException( "Divisor cannot be zero" );
+    public static int quotient(int number1, int number2) {
+        if (number2 == 0) {
+            throw new ArithmeticException("Divisor cannot be zero");
         }
 
         return number1 / number2;
     }
 
-    public static void main( String[] args ) {
-        Scanner input = new Scanner( System.in );
+    public static void main(String[] args) {
+        Scanner input = new Scanner(System.in);
 
         // Prompt the user to enter two integers
-        System.out.print( "Enter two integers: " );
+        System.out.print("Enter two integers: ");
         int number1 = input.nextInt();
         int number2 = input.nextInt();
 
         try {
-            int result = quotient( number1, number2 );
-            System.out.println( number1 + " / " + number2 + " is "
-                    + result );
-        } catch ( ArithmeticException ex ) {
-            System.out.println( "Exception: an integer "
-                    + "cannot be divided by zero " );
+            int result = quotient(number1, number2);
+            System.out.println(number1 + " / " + number2 + " is "
+                    + result);
+        } catch (ArithmeticException ex) {
+            System.out.println("Exception: an integer "
+                    + "cannot be divided by zero ");
         }
 
-        System.out.println( "Execution continues ..." );
+        System.out.println("Execution continues ...");
     }
 }

topics/code/trywith/src/Trywith.java

@@ -11,21 +11,21 @@
  */
 public class Trywith {
 
-    public static void main( String[] args ) throws IOException {
+    public static void main(String[] args) throws IOException {
 
         try (
-          File f = new File( "data.txt" );
+          File f = new File("data.txt");
           Scanner scanner = new Scanner(f); //<1>
         ) {
           String s1 = scanner.next();
-        } catch ( FileNotFoundException fnfe ) {
+        } catch (FileNotFoundException fnfe) {
             // deal with exceptions.
         } //<2>
     }
 
     interface Ikk{
         private static void hello(){
-            System.out.println( "Hello" );
+            System.out.println("Hello");
         }
     }
 }

topics/exceptions.adoc

@@ -148,10 +148,10 @@ Although you cannot simply iterate through these exceptions, getting all in a lo
 [source,java]
 ----
 Throwable t = ex.getCause();
-while ( t != null ) {
+while (t != null) {
   // do something with t like print or getMessage;
 
-  t= t.getCause();
+  t = t.getCause();
 }
 ----
 

topics/internationalisation.adoc

@@ -50,20 +50,20 @@ so that the whole test method reads
 [source,java]
 ----
 @ParameterizedTest
-@CsvSource( {
+@CsvSource({
     "a,greenCircle,blueCircle,500.0,400.0,100.0,100.0,500.0",
     "b,redCircle,blueCircle,400.0,100.0,100.0,100.0,500.0",
-    "c,greenCircle,redCircle,300.0,100.0,100.0,400.0,100.0", } )
-public void tLength( String line, String p1, String p2, double expected,
-        double x1, double y1, double x2, double y2 ) throws ParseException {
+    "c,greenCircle,redCircle,300.0,100.0,100.0,400.0,100.0", })
+public void tLength(String line, String p1, String p2, double expected,
+        double x1, double y1, double x2, double y2) throws ParseException {
     double xOrg = stage.getX();
     double yOrg = stage.getY();
     FxRobot rob = new FxRobot();
-    rob.drag( '#' + p1 ).dropTo( xOrg + x1, yOrg + y1 );
-    rob.drag( '#' + p2 ).dropTo( xOrg + x2, yOrg + y2 );
-    String ltext = labelMap.get( line ).apply( triangulator ).getText();
-    double l = getDoubleConsideringLocale( ltext.split( ":" )[ 1 ] ); // <1>
-    assertThat( l ).isCloseTo( expected, within( 0.1 ) );
+    rob.drag('#' + p1).dropTo(xOrg + x1, yOrg + y1);
+    rob.drag('#' + p2).dropTo(xOrg + x2, yOrg + y2);
+    String ltext = labelMap.get(line).apply(triangulator).getText();
+    double l = getDoubleConsideringLocale(ltext.split(":")[1]); // <1>
+    assertThat(l).isCloseTo(expected, within(0.1));
 //        fail( "method tLength reached end. You know what to do." );
 }
 ----
@@ -79,9 +79,9 @@ public void tLength( String line, String p1, String p2, double expected,
     * @return the double
     * @throws ParseException if the string does not parse to double.
     */
-static double getDoubleConsideringLocale( String input )
+static double getDoubleConsideringLocale(String input)
    throws ParseException {
-    return DecimalFormat.getNumberInstance().parse( input ).doubleValue(); // <1>
+    return DecimalFormat.getNumberInstance().parse(input).doubleValue(); // <1>
 }
 
 /**
@@ -91,14 +91,9 @@ static double getDoubleConsideringLocale( String input )
 * @return the double.
 * @throws ParseException if the string does not parse to double.
 */
-<<<<<<< Updated upstream
-static double getDoubleConsideringLocale( Locale locale, String input )
+static double getDoubleConsideringLocale(Locale locale, String input)
     throws ParseException {
-=======
-static double getDoubleConsideringLocale( Locale locale, String input )
-  throws ParseException {
->>>>>>> Stashed changes
-    return DecimalFormat.getNumberInstance(locale).parse( input ).doubleValue();
+    return DecimalFormat.getNumberInstance(locale).parse(input).doubleValue();
 }
 ----
 
@@ -107,12 +102,54 @@ static double getDoubleConsideringLocale( Locale locale, String input )
 .Set the locale for the execution. Useful for tests.
 [source,java]
 ----
-Locale.setDefault( Locale.GERMANY ); // <1>
+Locale.setDefault(Locale.GERMANY); // <1>
 ----
 
 <1> Set the locale to GERMANY if it isn't already. Similar for other languages.
 
 
+=== ResourceBundle and MessageFormat
+
+Java's `ResourceBundle` is the standard mechanism for externalising locale-specific strings into `.properties` files.
+Place one base file plus one file per supported locale under `src/main/resources`:
+
+----
+src/main/resources/pub/inthepub.properties          ← default (English)
+src/main/resources/pub/inthepub_nl_NL.properties    ← Dutch
+src/main/resources/pub/inthepub_de_DE.properties    ← German
+----
+
+A `.properties` file is a plain key=value text file.
+Keys that contain `{0}`, `{1}`, … are parameterised placeholders:
+
+.greetings.properties
+[source,properties]
+----
+greeting=Hello, {0}!
+farewell=Goodbye, {0}. See you on {1}.
+----
+
+To load the bundle for the current locale and look up a key at runtime:
+
+.Looking up and formatting a localized message
+[source,java]
+----
+ResourceBundle bundle = ResourceBundle.getBundle(
+        "greetings",          // <1>
+        Locale.getDefault()); // <2>
+if (bundle.containsKey("greeting")) {                        // <3>
+    String pattern = bundle.getString("greeting");
+    String message = MessageFormat.format(pattern, "World"); // <4>
+}
+----
+
+<1> Base name of the properties file (no extension, no locale suffix) — Java appends `_nl_NL` etc. automatically.
+<2> Use the current default locale. Change it with `Locale.setDefault(...)`, e.g. in a test.
+<3> `containsKey` guards against `MissingResourceException` when a key is absent.
+<4> `MessageFormat.format` substitutes `{0}`, `{1}`, … with the supplied arguments.
+
+The JVM picks the most specific file available: `inthepub_nl_NL.properties` → `inthepub_nl.properties` → `inthepub.properties` (fallback).
+
 === Testing Localized Exceptions
 
 The standard way of testing exceptions with assertj is explained in link:week01.html#_assert_exceptions[week01].
@@ -121,23 +158,22 @@ To get to the localized message, which contains the message as translated by the
 
 Luckily, AssertJ allows you to extract information from a Throwable, by using an extractor function. Now the Lambda bells should ring.
 
-.To make a long story very short: here is an example:
+.To make a long story very short: here is an example (using the pub exercise domain):
 [source,java]
 ----
-String[] keys = keyWords.split( "\\|");
-assertThatThrownBy( () -> {
-            MainSimulation.main( args );
-} ).isExactlyInstanceOf( exceptionMap.get( expectionClassName ) )
-        .extracting( e -> e.getLocalizedMessage() ) // <1>
+Locale.setDefault(Locale.forLanguageTag("nl-NL"));
+assertThatThrownBy(() -> barkeeper.serve(drinker, volume))
+        .isExactlyInstanceOf(EmptyStockException.class)
+        .extracting(e -> e.getLocalizedMessage()) // <1>
         .asString()           //<2>
-        .contains( keys ); //<3>
+        .contains("uitverkocht"); //<3>
 ----
 
 <1> extract using [blue]`Function<? super Throwable,​T>`, [black]`e -> getLocalizedMessage()` in this case.
 <2> Get the assertion for in String. Do [red]*not* use `toString()`, because that produces a _String_, not an [blue]*AbstractStringAssert*.
 <3> And use the assert to check that the string contains the required key information.
 
-.If you turn on type hints in NetBeans-IDE (or in vscode/intelij) you can see what the type is on which you call `contains(keys)`
+.If you turn on type hints in NetBeans-IDE (or in VS Code/IntelliJ) you can see what the type is on which you call `contains(keys)`
 image::assertjtypehints.png
 
 

topics/logging.adoc

@@ -5,11 +5,11 @@ Logging can be a very powerful instrument to squeeze very much or very precise i
 .Using a supplier suppresses the generation of the log when the log level is not active.
 [source,java]
 ----
-public static void main( String[] args ) {
-    Logger logger = Logger.getLogger( Main.class.getName() ); // <1>
-    logger.log( Level.FINE,                                   // <2>
-       ()-> String.format("Hello %1$s args length= %2$d ",    //<3>
-                          "world", args.length)               //<4>
+public static void main(String[] args) {
+    Logger logger = Logger.getLogger(Main.class.getName()); // <1>
+    logger.log(Level.FINE,                                  // <2>
+       ()-> String.format("Hello %1$s args length= %2$d ",  //<3>
+                          "world", args.length)             //<4>
     );
 }
 ----
@@ -73,6 +73,27 @@ image::logging-activation.png[title="Project specific logging in NetBeans IDE"]
 
 ====
 
+=== Logging with i18n messages
+
+You can combine logging with `ResourceBundle` and `MessageFormat` to produce localised log messages.
+This is useful when the locale may change between runs (e.g. per user or per test).
+
+.Log a message using a ResourceBundle key and MessageFormat
+[source,java]
+----
+ResourceBundle bundle = ResourceBundle.getBundle(
+        "greetings", Locale.getDefault());
+String pattern = bundle.getString("farewell");                           // <1>
+String date    = LocalDate.now().format(
+        DateTimeFormatter.ofLocalizedDate(FormatStyle.FULL));            // <2>
+logger.log(Level.INFO, () ->
+        MessageFormat.format(pattern, "World", date));                   // <3>
+----
+
+<1> Look up the localised pattern from the bundle; `farewell=Goodbye, {0}. See you on {1}.` in the default locale.
+<2> Format today's date according to the current locale (e.g. `"Monday, 11 May 2026"` in English).
+<3> Supply the lambda so the string is only built when the INFO level is actually active.
+
 Read a bit more about logging in the book and get some additional information using https://sematext.com/blog/java-logging/.