[Core] Use Locale.ROOT when transforming case of identifiers

Several plugins use lowercased string representations of enum
values. Doing this without an explicit locale results in the
default locale being used. This may lead to surprising errors.

Fixes: cucumber/cucumber-java-skeleton#33

core/src/main/java/cucumber/api/HookType.java

@@ -1,10 +1,12 @@
 package cucumber.api;
 
+import static java.util.Locale.ROOT;
+
 public enum HookType {
     Before, After, BeforeStep, AfterStep;
 
     @Override
     public String toString() {
-        return super.toString().toLowerCase();
+        return super.toString().toLowerCase(ROOT);
     }
 }

core/src/main/java/cucumber/api/Result.java

@@ -5,6 +5,7 @@
 import java.util.Comparator;
 import java.util.Objects;
 
+import static java.util.Locale.ROOT;
 import static java.util.Objects.requireNonNull;
 
 public final class Result {
@@ -30,15 +31,15 @@ public enum Type {
         FAILED;
 
         public static Type fromLowerCaseName(String lowerCaseName) {
-            return valueOf(lowerCaseName.toUpperCase());
+            return valueOf(lowerCaseName.toUpperCase(ROOT));
         }
 
         public String lowerCaseName() {
-            return name().toLowerCase();
+            return name().toLowerCase(ROOT);
         }
 
         public String firstLetterCapitalizedName() {
-            return name().substring(0, 1) + name().substring(1).toLowerCase();
+            return name().substring(0, 1) + name().substring(1).toLowerCase(ROOT);
         }
 
 

core/src/main/java/cucumber/runtime/Env.java

@@ -6,6 +6,8 @@
 import java.util.Properties;
 import java.util.ResourceBundle;
 
+import static java.util.Locale.ROOT;
+
 /**
  * Looks up values in the following order:
  * <ol>
@@ -56,8 +58,8 @@ public Env(String bundleName, Properties properties) {
     private void put(String key, String string) {
         map.put(key, string);
         // Support old skool
-        map.put(key.replace('.', '_').toUpperCase(), string);
-        map.put(key.replace('_', '.').toLowerCase(), string);
+        map.put(key.replace('.', '_').toUpperCase(ROOT), string);
+        map.put(key.replace('_', '.').toLowerCase(ROOT), string);
     }
 
     public String get(String key) {

core/src/main/java/cucumber/util/Encoding.java

@@ -7,6 +7,8 @@
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import static java.util.Locale.ROOT;
+
 /**
  * Utilities for reading the encoding of a file.
  */
@@ -36,6 +38,6 @@ private static String encoding(String source) {
                 break;
             }
         }
-        return encoding.toUpperCase();
+        return encoding.toUpperCase(ROOT);
     }
 }

junit/src/main/java/cucumber/runtime/junit/NotificationLevel.java

@@ -1,10 +1,12 @@
 package cucumber.runtime.junit;
 
+import static java.util.Locale.ROOT;
+
 public enum NotificationLevel {
     SCENARIO,
     STEP;
 
     String lowerCaseName() {
-        return name().toLowerCase();
+        return name().toLowerCase(ROOT);
     }
 }