fix NPE in category tree factory

Closes #1033

Author: jenschude

commercetools/commercetools-sdk-java-api/src/main/java/com/commercetools/api/models/category/CategoryTreeFactory.java

@@ -64,7 +64,7 @@ private Map<LocalizedStringEntry, Category> getLocalizedStringEntryCategoryMap(
                     .values()
                     .keySet()
                     .stream()
-                    .map(Locale::new)
+                    .map(Locale::forLanguageTag)
                     .collect(Collectors.toSet());
             localesForTheCategory.forEach(locale -> {
                 final LocalizedStringEntry stringsEntry = LocalizedStringEntry.of(locale,

commercetools/commercetools-sdk-java-api/src/test/java/com/commercetools/CategoriesTest.java

@@ -66,4 +66,64 @@ public void testCategoryTree() {
         var result = tree.findBySlug(Locale.ENGLISH, "women");
         Assertions.assertThat(result).isNotEmpty();
     }
+
+    @Test
+    public void testGetLocalizedStringEntryCategoryMap()
+    {
+        List<Category> allCategoriesAsFlatList = List.of(
+                Category.builder()
+                    .name(LocalizedString.of(Locale.forLanguageTag("en-US"), "Women"))
+                    .slug(LocalizedString.of(Locale.forLanguageTag("en-US"), "women"))
+                    .id("1")
+                    .version(1L)
+                    .createdAt(ZonedDateTime.now())
+                    .lastModifiedAt(ZonedDateTime.now())
+                    .ancestors()
+                    .orderHint("c2")
+                .build(),
+                Category.builder()
+                        .name(LocalizedString.of(Locale.forLanguageTag("en"), "Men"))
+                        .slug(LocalizedString.of(Locale.forLanguageTag("en"), "men"))
+                        .id("2")
+                        .version(1L)
+                        .createdAt(ZonedDateTime.now())
+                        .lastModifiedAt(ZonedDateTime.now())
+                        .ancestors()
+                        .orderHint("c2")
+                        .build(),
+                Category.builder()
+                        .name(LocalizedString.of(Locale.forLanguageTag("en-us"), "Kids"))
+                        .slug(LocalizedString.of(Locale.forLanguageTag("en-us"), "kids"))
+                        .id("3")
+                        .version(1L)
+                        .createdAt(ZonedDateTime.now())
+                        .lastModifiedAt(ZonedDateTime.now())
+                        .ancestors()
+                        .orderHint("c2")
+                        .build());
+        CategoryTreeFactory factory = CategoryTreeFactory.of();
+
+        var tree = factory.create(allCategoriesAsFlatList);
+        var result = tree.findBySlug(Locale.forLanguageTag("en-US"), "women");
+        Assertions.assertThat(result).isNotEmpty();
+        var enUsResult = tree.findBySlug(Locale.forLanguageTag("en-us"), "women");
+        Assertions.assertThat(enUsResult).isNotEmpty();
+
+        var enResult = tree.findBySlug(Locale.forLanguageTag("en"), "women");
+        Assertions.assertThat(enResult).isEmpty();
+
+        var menResult = tree.findBySlug(Locale.forLanguageTag("en-US"), "men");
+        Assertions.assertThat(menResult).isEmpty();
+        var menEnUsResult = tree.findBySlug(Locale.forLanguageTag("en-us"), "men");
+        Assertions.assertThat(menEnUsResult).isEmpty();
+        var menEnResult = tree.findBySlug(Locale.forLanguageTag("en"), "men");
+        Assertions.assertThat(menEnResult).isNotEmpty();
+
+        var kidsResult = tree.findBySlug(Locale.forLanguageTag("en-US"), "kids");
+        Assertions.assertThat(kidsResult).isNotEmpty();
+        var kidsEnUsResult = tree.findBySlug(Locale.forLanguageTag("en-us"), "kids");
+        Assertions.assertThat(kidsEnUsResult).isNotEmpty();
+        var kidsEnResult = tree.findBySlug(Locale.forLanguageTag("en"), "kids");
+        Assertions.assertThat(kidsEnResult).isEmpty();
+    }
 }