strings' externalization - simple step to multi-lingual options help

src/main/java/joptsimple/BuiltinHelpFormatter.java

@@ -46,9 +46,9 @@ class BuiltinHelpFormatter implements HelpFormatter {
 
     public String format( Map<String, ? extends OptionDescriptor> options ) {
         if ( options.isEmpty() )
-            return "No options specified";
+            return Messages.getString( "BuiltinHelpFormatter.noOptionsSpecified" );
 
-        grid = new ColumnarData( optionHeader( options ), "Description" );
+        grid = new ColumnarData( optionHeader( options ), Messages.getString( "BuiltinHelpFormatter.description" ) );
 
         Comparator<OptionDescriptor> comparator =
             new Comparator<OptionDescriptor>() {
@@ -69,10 +69,10 @@ public int compare( OptionDescriptor first, OptionDescriptor second ) {
     private String optionHeader( Map<String, ? extends OptionDescriptor> options ) {
         for ( OptionDescriptor each : options.values() ) {
             if ( each.isRequired() )
-                return "Option (* = required)";
+                return Messages.getString( "BuiltinHelpFormatter.optionRequired" );
         }
 
-        return "Option";
+        return Messages.getString( "BuiltinHelpFormatter.option" );
     }
 
     private void addHelpLineFor( OptionDescriptor descriptor ) {
@@ -131,7 +131,7 @@ private String createDescriptionDisplay( OptionDescriptor descriptor ) {
             return descriptor.description();
 
         String defaultValuesDisplay = createDefaultValuesDisplay( defaultValues );
-        return descriptor.description() + ' ' + surround( "default: " + defaultValuesDisplay, '(', ')' );
+        return descriptor.description() + ' ' + surround( Messages.getString( "BuiltinHelpFormatter.default" ) + defaultValuesDisplay, '(', ')' );
     }
 
     private String createDefaultValuesDisplay( List<?> defaultValues ) {

src/main/java/joptsimple/Messages.java

@@ -0,0 +1,22 @@
+package joptsimple;
+
+import java.util.Locale;
+import java.util.MissingResourceException;
+import java.util.ResourceBundle;
+
+public class Messages {
+    private static final String BUNDLE_NAME = "joptsimple.messages";
+
+    private static final ResourceBundle RESOURCE_BUNDLE = ResourceBundle.getBundle( BUNDLE_NAME, Locale.getDefault() );
+
+    private Messages() {
+    }
+
+    public static String getString( String key ) {
+        try {
+            return RESOURCE_BUNDLE.getString( key );
+        } catch ( MissingResourceException e ) {
+            return '!' + key + '!';
+        }
+    }
+}

src/main/java/joptsimple/messages.properties

@@ -0,0 +1,5 @@
+BuiltinHelpFormatter.default=default: 
+BuiltinHelpFormatter.description=Description
+BuiltinHelpFormatter.noOptionsSpecified=No options specified
+BuiltinHelpFormatter.option=Option
+BuiltinHelpFormatter.optionRequired=Option (* = required)

src/main/java/joptsimple/messages_en_US.properties

@@ -0,0 +1,5 @@
+BuiltinHelpFormatter.default=default: 
+BuiltinHelpFormatter.description=Description
+BuiltinHelpFormatter.noOptionsSpecified=No options specified
+BuiltinHelpFormatter.option=Option
+BuiltinHelpFormatter.optionRequired=Option (* = required)

src/main/java/joptsimple/messages_pl_PL.properties

@@ -0,0 +1,5 @@
+BuiltinHelpFormatter.default=domy\u015Blnie: 
+BuiltinHelpFormatter.description=Opis
+BuiltinHelpFormatter.noOptionsSpecified=Brak opcji
+BuiltinHelpFormatter.option=Opcja
+BuiltinHelpFormatter.optionRequired=Opcja (* = wymagana)