[BAEL-1536] A Guide to the Resource Bundle (#3602)

* [BAEL-1536] A Guide to the Resource Bundle

The essential code for the article

* [BAEL-1536] A Guide to the Resource Bundle #2

The essential code for the article after the first article review.

* [BAEL-1536] A Guide to the Resource Bundle #3

Essential changes after the second review.

* [BAEL-1536] A Guide to the Resource Bundle #4

Essential changes after the second review:
- Doubles to BigDecimals

core-java/src/main/java/com/baeldung/resourcebundle/ExampleControl.java

@@ -0,0 +1,15 @@
+package com.baeldung.resourcebundle;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Locale;
+import java.util.ResourceBundle;
+
+public class ExampleControl extends ResourceBundle.Control {
+
+    @Override
+    public List<Locale> getCandidateLocales(String s, Locale locale) {
+        return Arrays.asList(new Locale("pl", "PL"));
+    }
+
+}

core-java/src/main/java/com/baeldung/resourcebundle/ExampleResource.java

@@ -0,0 +1,14 @@
+package com.baeldung.resourcebundle;
+
+import java.util.ListResourceBundle;
+
+public class ExampleResource extends ListResourceBundle {
+
+    @Override
+    protected Object[][] getContents() {
+        return new Object[][] { 
+            { "greeting", "hello" } 
+        };
+    }
+
+}

core-java/src/main/java/com/baeldung/resourcebundle/ExampleResource_pl.java

@@ -0,0 +1,15 @@
+package com.baeldung.resourcebundle;
+
+import java.util.ListResourceBundle;
+
+public class ExampleResource_pl extends ListResourceBundle {
+
+    @Override
+    protected Object[][] getContents() {
+        return new Object[][] { 
+            { "greeting", "cześć" }, 
+            { "language", "polish" }, 
+        };
+    }
+
+}

core-java/src/main/java/com/baeldung/resourcebundle/ExampleResource_pl_PL.java

@@ -0,0 +1,17 @@
+package com.baeldung.resourcebundle;
+
+import java.math.BigDecimal;
+import java.util.ListResourceBundle;
+
+public class ExampleResource_pl_PL extends ListResourceBundle {
+
+    @Override
+    protected Object[][] getContents() {
+        return new Object[][] { 
+            { "currency", "polish zloty" }, 
+            { "toUsdRate", new BigDecimal("3.401") },
+            { "cities", new String[] { "Warsaw", "Cracow" } } 
+        };
+    }
+
+}

core-java/src/main/resources/resourcebundle/resource.properties

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+# Buttons
+cancelButton=cancel
+continueButton continue
+
+! Labels
+helloLabel:hello

core-java/src/main/resources/resourcebundle/resource_en.properties

@@ -0,0 +1 @@
+deleteButton=delete

core-java/src/main/resources/resourcebundle/resource_pl_PL.properties

@@ -0,0 +1,3 @@
+backButton=cofnij
+helloLabel=cze\u015b\u0107
+helloLabelNoEncoding=cześć

core-java/src/test/java/com/baeldung/resourcebundle/ExampleResourceUnitTest.java

@@ -0,0 +1,39 @@
+package com.baeldung.resourcebundle;
+
+import org.junit.Test;
+
+import java.math.BigDecimal;
+import java.util.Arrays;
+import java.util.Locale;
+import java.util.ResourceBundle;
+
+import static org.junit.Assert.*;
+
+public class ExampleResourceUnitTest {
+
+    @Test
+    public void whenGetBundleExampleResourceForLocalePlPl_thenItShouldInheritPropertiesGreetingAndLanguage() {
+        Locale plLocale = new Locale("pl", "PL");
+
+        ResourceBundle exampleBundle = ResourceBundle.getBundle("com.baeldung.resourcebundle.ExampleResource", plLocale);
+
+        assertTrue(exampleBundle.keySet()
+            .containsAll(Arrays.asList("toUsdRate", "cities", "greeting", "currency", "language")));
+        assertEquals(exampleBundle.getString("greeting"), "cześć");
+        assertEquals(exampleBundle.getObject("toUsdRate"), new BigDecimal("3.401"));
+        assertArrayEquals(exampleBundle.getStringArray("cities"), new String[] { "Warsaw", "Cracow" });
+    }
+
+    @Test
+    public void whenGetBundleExampleResourceForLocaleUs_thenItShouldContainOnlyGreeting() {
+        Locale usLocale = Locale.US;
+
+        ResourceBundle exampleBundle = ResourceBundle.getBundle("com.baeldung.resourcebundle.ExampleResource", usLocale);
+
+        assertFalse(exampleBundle.keySet()
+            .containsAll(Arrays.asList("toUsdRate", "cities", "currency", "language")));
+        assertTrue(exampleBundle.keySet()
+            .containsAll(Arrays.asList("greeting")));
+    }
+
+}

core-java/src/test/java/com/baeldung/resourcebundle/PropertyResourceUnitTest.java

@@ -0,0 +1,62 @@
+package com.baeldung.resourcebundle;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Locale;
+import java.util.ResourceBundle;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class PropertyResourceUnitTest {
+
+    @Test
+    public void givenLocaleUsAsDefualt_whenGetBundleForLocalePlPl_thenItShouldContain3ButtonsAnd1Label() {
+        Locale.setDefault(Locale.US);
+
+        ResourceBundle bundle = ResourceBundle.getBundle("resourcebundle.resource", new Locale("pl", "PL"));
+
+        assertTrue(bundle.keySet()
+            .containsAll(Arrays.asList("backButton", "helloLabel", "cancelButton", "continueButton", "helloLabelNoEncoding")));
+    }
+
+    @Test
+    public void givenLocaleUsAsDefualt_whenGetBundleForLocaleFrFr_thenItShouldContainKeys1To3AndKey4() {
+        Locale.setDefault(Locale.US);
+
+        ResourceBundle bundle = ResourceBundle.getBundle("resourcebundle.resource", new Locale("fr", "FR"));
+
+        assertTrue(bundle.keySet()
+            .containsAll(Arrays.asList("deleteButton", "helloLabel", "cancelButton", "continueButton")));
+    }
+
+    @Test
+    public void givenLocaleChinaAsDefualt_whenGetBundleForLocaleFrFr_thenItShouldOnlyContainKeys1To3() {
+        Locale.setDefault(Locale.CHINA);
+
+        ResourceBundle bundle = ResourceBundle.getBundle("resourcebundle.resource", new Locale("fr", "FR"));
+
+        assertTrue(bundle.keySet()
+            .containsAll(Arrays.asList("continueButton", "helloLabel", "cancelButton")));
+    }
+
+    @Test
+    public void givenLocaleChinaAsDefualt_whenGetBundleForLocaleFrFrAndExampleControl_thenItShouldOnlyContainKey5() {
+        Locale.setDefault(Locale.CHINA);
+
+        ResourceBundle bundle = ResourceBundle.getBundle("resourcebundle.resource", new Locale("fr", "FR"), new ExampleControl());
+
+        assertTrue(bundle.keySet()
+            .containsAll(Arrays.asList("backButton", "helloLabel")));
+    }
+
+    @Test
+    public void givenValuesDifferentlyEncoded_whenGetBundleForLocalePlPl_thenItShouldContain3ButtonsAnd1Label() {
+        ResourceBundle bundle = ResourceBundle.getBundle("resourcebundle.resource", new Locale("pl", "PL"));
+
+        assertEquals(bundle.getString("helloLabel"), "cześć");
+        assertEquals(bundle.getString("helloLabelNoEncoding"), "czeÅ\u009BÄ\u0087");
+    }
+
+}