SPIGOT-7676: Enforce locale parameter in toLowerCase and toUpperCase method calls and always use root locale

By: DerFrZocker <derrieple@gmail.com>

paper-api/checkstyle.xml

@@ -32,6 +32,16 @@
         <property name="files" value=".*[\\/]src[\\/]test[\\/].*\.java$"/>
     </module>
 
+    <!-- See SPIGOT-7676: Enforce Locale, to prevent issues with turkish 'I' and similar -->
+    <module name="RegexpSingleline">
+        <property name="format" value="\.toUpperCase\(\s*\)" />
+        <property name="message" value="Use toUpperCase(Locale.ROOT) instead of toUpperCase()" />
+    </module>
+    <module name="RegexpSingleline">
+        <property name="format" value="\.toLowerCase\(\s*\)" />
+        <property name="message" value="Use toLowerCase(Locale.ROOT) instead of toLowerCase()" />
+    </module>
+
     <module name="TreeWalker">
         <!-- See https://checkstyle.org/config_javadoc.html -->
         <module name="AtclauseOrder"/>

paper-api/src/main/java/org/bukkit/Art.java

@@ -3,6 +3,7 @@ package org.bukkit;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.Maps;
 import java.util.HashMap;
+import java.util.Locale;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -50,7 +51,7 @@ public enum Art implements Keyed {
         this.id = id;
         this.width = width;
         this.height = height;
-        this.key = NamespacedKey.minecraft(name().toLowerCase(java.util.Locale.ENGLISH));
+        this.key = NamespacedKey.minecraft(name().toLowerCase(Locale.ROOT));
     }
 
     /**
@@ -113,13 +114,13 @@ public enum Art implements Keyed {
     public static Art getByName(@NotNull String name) {
         Preconditions.checkArgument(name != null, "Name cannot be null");
 
-        return BY_NAME.get(name.toLowerCase(java.util.Locale.ENGLISH));
+        return BY_NAME.get(name.toLowerCase(Locale.ROOT));
     }
 
     static {
         for (Art art : values()) {
             BY_ID.put(art.id, art);
-            BY_NAME.put(art.toString().toLowerCase(java.util.Locale.ENGLISH), art);
+            BY_NAME.put(art.toString().toLowerCase(Locale.ROOT), art);
         }
     }
 }

paper-api/src/main/java/org/bukkit/Color.java

@@ -3,6 +3,7 @@ package org.bukkit;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableMap;
 import java.util.Arrays;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import org.bukkit.configuration.serialization.ConfigurationSerializable;
@@ -428,6 +429,6 @@ public final class Color implements ConfigurationSerializable {
 
     @Override
     public String toString() {
-        return "Color:[argb0x" + Integer.toHexString(asARGB()).toUpperCase() + "]";
+        return "Color:[argb0x" + Integer.toHexString(asARGB()).toUpperCase(Locale.ROOT) + "]";
     }
 }

paper-api/src/main/java/org/bukkit/Material.java

@@ -4954,7 +4954,7 @@ public enum Material implements Keyed, Translatable {
             filtered = filtered.substring((NamespacedKey.MINECRAFT + ":").length());
         }
 
-        filtered = filtered.toUpperCase(java.util.Locale.ENGLISH);
+        filtered = filtered.toUpperCase(Locale.ROOT);
 
         filtered = filtered.replaceAll("\\s+", "_").replaceAll("\\W", "");
         return getMaterial(filtered, legacyName);

paper-api/src/main/java/org/bukkit/Registry.java

@@ -4,6 +4,7 @@ import com.google.common.base.Preconditions;
 import com.google.common.base.Predicates;
 import com.google.common.collect.ImmutableMap;
 import java.util.Iterator;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.function.Predicate;
@@ -333,7 +334,7 @@ public interface Registry<T extends Keyed> extends Iterable<T> {
     default T match(@NotNull String input) {
         Preconditions.checkArgument(input != null, "input must not be null");
 
-        String filtered = input.toLowerCase().replaceAll("\\s+", "_");
+        String filtered = input.toLowerCase(Locale.ROOT).replaceAll("\\s+", "_");
         NamespacedKey namespacedKey = NamespacedKey.fromString(filtered);
         return (namespacedKey != null) ? get(namespacedKey) : null;
     }

paper-api/src/main/java/org/bukkit/Warning.java

@@ -5,6 +5,7 @@ import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
+import java.util.Locale;
 import java.util.Map;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -86,7 +87,7 @@ public @interface Warning {
             if (value == null) {
                 return DEFAULT;
             }
-            WarningState state = values.get(value.toLowerCase());
+            WarningState state = values.get(value.toLowerCase(Locale.ROOT));
             if (state == null) {
                 return DEFAULT;
             }

paper-api/src/main/java/org/bukkit/WorldType.java

@@ -1,6 +1,7 @@
 package org.bukkit;
 
 import com.google.common.collect.Maps;
+import java.util.Locale;
 import java.util.Map;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -39,7 +40,7 @@ public enum WorldType {
      */
     @Nullable
     public static WorldType getByName(@NotNull String name) {
-        return BY_NAME.get(name.toUpperCase(java.util.Locale.ENGLISH));
+        return BY_NAME.get(name.toUpperCase(Locale.ROOT));
     }
 
     static {

paper-api/src/main/java/org/bukkit/attribute/AttributeModifier.java

@@ -2,6 +2,7 @@ package org.bukkit.attribute;
 
 import com.google.common.base.Preconditions;
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.UUID;
@@ -159,11 +160,11 @@ public class AttributeModifier implements ConfigurationSerializable {
     @NotNull
     public static AttributeModifier deserialize(@NotNull Map<String, Object> args) {
         if (args.containsKey("slot")) {
-            EquipmentSlotGroup slotGroup = EquipmentSlotGroup.getByName(args.get("slot").toString().toLowerCase());
+            EquipmentSlotGroup slotGroup = EquipmentSlotGroup.getByName(args.get("slot").toString().toLowerCase(Locale.ROOT));
             if (slotGroup == null) {
                 slotGroup = EquipmentSlotGroup.ANY;
 
-                EquipmentSlot slot = EquipmentSlot.valueOf((args.get("slot").toString().toUpperCase()));
+                EquipmentSlot slot = EquipmentSlot.valueOf((args.get("slot").toString().toUpperCase(Locale.ROOT)));
                 if (slot != null) {
                     slotGroup = slot.getGroup();
                 }

paper-api/src/main/java/org/bukkit/command/SimpleCommandMap.java

@@ -8,6 +8,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import org.bukkit.Location;
 import org.bukkit.Server;
@@ -67,8 +68,8 @@ public class SimpleCommandMap implements CommandMap {
      */
     @Override
     public boolean register(@NotNull String label, @NotNull String fallbackPrefix, @NotNull Command command) {
-        label = label.toLowerCase(java.util.Locale.ENGLISH).trim();
+        label = label.toLowerCase(Locale.ROOT).trim();
-        fallbackPrefix = fallbackPrefix.toLowerCase(java.util.Locale.ENGLISH).trim();
+        fallbackPrefix = fallbackPrefix.toLowerCase(Locale.ROOT).trim();
         boolean registered = register(label, command, false, fallbackPrefix);
 
         Iterator<String> iterator = command.getAliases().iterator();
@@ -136,7 +137,7 @@ public class SimpleCommandMap implements CommandMap {
             return false;
         }
 
-        String sentCommandLabel = args[0].toLowerCase(java.util.Locale.ENGLISH);
+        String sentCommandLabel = args[0].toLowerCase(Locale.ROOT);
         Command target = getCommand(sentCommandLabel);
 
         if (target == null) {
@@ -168,7 +169,7 @@ public class SimpleCommandMap implements CommandMap {
     @Override
     @Nullable
     public Command getCommand(@NotNull String name) {
-        Command target = knownCommands.get(name.toLowerCase(java.util.Locale.ENGLISH));
+        Command target = knownCommands.get(name.toLowerCase(Locale.ROOT));
         return target;
     }
 
@@ -272,9 +273,9 @@ public class SimpleCommandMap implements CommandMap {
 
             // We register these as commands so they have absolute priority.
             if (targets.size() > 0) {
-                knownCommands.put(alias.toLowerCase(java.util.Locale.ENGLISH), new FormattedCommandAlias(alias.toLowerCase(java.util.Locale.ENGLISH), targets.toArray(new String[targets.size()])));
+                knownCommands.put(alias.toLowerCase(Locale.ROOT), new FormattedCommandAlias(alias.toLowerCase(Locale.ROOT), targets.toArray(new String[targets.size()])));
             } else {
-                knownCommands.remove(alias.toLowerCase(java.util.Locale.ENGLISH));
+                knownCommands.remove(alias.toLowerCase(Locale.ROOT));
             }
         }
     }

paper-api/src/main/java/org/bukkit/command/defaults/VersionCommand.java

@@ -15,6 +15,7 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Locale;
 import java.util.Set;
 import java.util.concurrent.locks.ReentrantLock;
 import org.bukkit.Bukkit;
@@ -61,9 +62,9 @@ public class VersionCommand extends BukkitCommand {
             }
 
             boolean found = false;
-            pluginName = pluginName.toLowerCase(java.util.Locale.ENGLISH);
+            pluginName = pluginName.toLowerCase(Locale.ROOT);
             for (Plugin plugin : Bukkit.getPluginManager().getPlugins()) {
-                if (plugin.getName().toLowerCase(java.util.Locale.ENGLISH).contains(pluginName)) {
+                if (plugin.getName().toLowerCase(Locale.ROOT).contains(pluginName)) {
                     describeToSender(plugin, sender);
                     found = true;
                 }
@@ -133,7 +134,7 @@ public class VersionCommand extends BukkitCommand {
 
         if (args.length == 1) {
             List<String> completions = new ArrayList<String>();
-            String toComplete = args[0].toLowerCase(java.util.Locale.ENGLISH);
+            String toComplete = args[0].toLowerCase(Locale.ROOT);
             for (Plugin plugin : Bukkit.getPluginManager().getPlugins()) {
                 if (StringUtil.startsWithIgnoreCase(plugin.getName(), toComplete)) {
                     completions.add(plugin.getName());

paper-api/src/main/java/org/bukkit/enchantments/Enchantment.java

@@ -2,6 +2,7 @@ package org.bukkit.enchantments;
 
 import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
+import java.util.Locale;
 import org.bukkit.Keyed;
 import org.bukkit.MinecraftExperimental;
 import org.bukkit.MinecraftExperimental.Requires;
@@ -351,7 +352,7 @@ public abstract class Enchantment implements Keyed, Translatable {
             return null;
         }
 
-        return getByKey(NamespacedKey.fromString(name.toLowerCase()));
+        return getByKey(NamespacedKey.fromString(name.toLowerCase(Locale.ROOT)));
     }
 
     /**

paper-api/src/main/java/org/bukkit/entity/EntityType.java

@@ -2,6 +2,7 @@ package org.bukkit.entity;
 
 import com.google.common.base.Preconditions;
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 import org.bukkit.Bukkit;
 import org.bukkit.Keyed;
@@ -331,7 +332,7 @@ public enum EntityType implements Keyed, Translatable {
     static {
         for (EntityType type : values()) {
             if (type.name != null) {
-                NAME_MAP.put(type.name.toLowerCase(java.util.Locale.ENGLISH), type);
+                NAME_MAP.put(type.name.toLowerCase(Locale.ROOT), type);
             }
             if (type.typeId > 0) {
                 ID_MAP.put(type.typeId, type);
@@ -402,7 +403,7 @@ public enum EntityType implements Keyed, Translatable {
         if (name == null) {
             return null;
         }
-        return NAME_MAP.get(name.toLowerCase(java.util.Locale.ENGLISH));
+        return NAME_MAP.get(name.toLowerCase(Locale.ROOT));
     }
 
     /**

paper-api/src/main/java/org/bukkit/inventory/EquipmentSlotGroup.java

@@ -2,6 +2,7 @@ package org.bukkit.inventory;
 
 import com.google.common.base.Preconditions;
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 import java.util.function.Predicate;
 import org.jetbrains.annotations.ApiStatus;
@@ -73,7 +74,7 @@ public final class EquipmentSlotGroup implements Predicate<EquipmentSlot> {
     public static EquipmentSlotGroup getByName(@NotNull String name) {
         Preconditions.checkArgument(name != null, "Name cannot be null");
 
-        return BY_NAME.get(name.toLowerCase(java.util.Locale.ENGLISH));
+        return BY_NAME.get(name.toLowerCase(Locale.ROOT));
     }
 
     private static EquipmentSlotGroup get(@NotNull String key, @NotNull EquipmentSlot slot) {

paper-api/src/main/java/org/bukkit/permissions/PermissibleBase.java

@@ -4,6 +4,7 @@ import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.logging.Level;
@@ -52,7 +53,7 @@ public class PermissibleBase implements Permissible {
             throw new IllegalArgumentException("Permission name cannot be null");
         }
 
-        return permissions.containsKey(name.toLowerCase(java.util.Locale.ENGLISH));
+        return permissions.containsKey(name.toLowerCase(Locale.ROOT));
     }
 
     @Override
@@ -70,7 +71,7 @@ public class PermissibleBase implements Permissible {
             throw new IllegalArgumentException("Permission name cannot be null");
         }
 
-        String name = inName.toLowerCase(java.util.Locale.ENGLISH);
+        String name = inName.toLowerCase(Locale.ROOT);
 
         if (isPermissionSet(name)) {
             return permissions.get(name).getValue();
@@ -91,7 +92,7 @@ public class PermissibleBase implements Permissible {
             throw new IllegalArgumentException("Permission cannot be null");
         }
 
-        String name = perm.getName().toLowerCase(java.util.Locale.ENGLISH);
+        String name = perm.getName().toLowerCase(Locale.ROOT);
 
         if (isPermissionSet(name)) {
             return permissions.get(name).getValue();
@@ -161,7 +162,7 @@ public class PermissibleBase implements Permissible {
         Bukkit.getServer().getPluginManager().subscribeToDefaultPerms(isOp(), parent);
 
         for (Permission perm : defaults) {
-            String name = perm.getName().toLowerCase(java.util.Locale.ENGLISH);
+            String name = perm.getName().toLowerCase(Locale.ROOT);
             permissions.put(name, new PermissionAttachmentInfo(parent, name, null, true));
             Bukkit.getServer().getPluginManager().subscribeToPermission(name, parent);
             calculateChildPermissions(perm.getChildren(), false, null);
@@ -191,7 +192,7 @@ public class PermissibleBase implements Permissible {
 
             Permission perm = Bukkit.getServer().getPluginManager().getPermission(name);
             boolean value = entry.getValue() ^ invert;
-            String lname = name.toLowerCase(java.util.Locale.ENGLISH);
+            String lname = name.toLowerCase(Locale.ROOT);
 
             permissions.put(lname, new PermissionAttachmentInfo(parent, lname, attachment, value));
             Bukkit.getServer().getPluginManager().subscribeToPermission(name, parent);

paper-api/src/main/java/org/bukkit/permissions/Permission.java

@@ -4,6 +4,7 @@ import com.google.common.base.Preconditions;
 import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.logging.Level;
@@ -186,7 +187,7 @@ public class Permission {
     @NotNull
     public Permission addParent(@NotNull String name, boolean value) {
         PluginManager pm = Bukkit.getServer().getPluginManager();
-        String lname = name.toLowerCase(java.util.Locale.ENGLISH);
+        String lname = name.toLowerCase(Locale.ROOT);
 
         Permission perm = pm.getPermission(lname);
 

paper-api/src/main/java/org/bukkit/permissions/PermissionAttachment.java

@@ -1,6 +1,7 @@
 package org.bukkit.permissions;
 
 import java.util.LinkedHashMap;
+import java.util.Locale;
 import java.util.Map;
 import org.bukkit.plugin.Plugin;
 import org.jetbrains.annotations.NotNull;
@@ -89,7 +90,7 @@ public class PermissionAttachment {
      * @param value New value of the permission
      */
     public void setPermission(@NotNull String name, boolean value) {
-        permissions.put(name.toLowerCase(java.util.Locale.ENGLISH), value);
+        permissions.put(name.toLowerCase(Locale.ROOT), value);
         permissible.recalculatePermissions();
     }
 
@@ -112,7 +113,7 @@ public class PermissionAttachment {
      * @param name Name of the permission to remove
      */
     public void unsetPermission(@NotNull String name) {
-        permissions.remove(name.toLowerCase(java.util.Locale.ENGLISH));
+        permissions.remove(name.toLowerCase(Locale.ROOT));
         permissible.recalculatePermissions();
     }
 

paper-api/src/main/java/org/bukkit/permissions/PermissionDefault.java

@@ -1,6 +1,7 @@
 package org.bukkit.permissions;
 
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -51,7 +52,7 @@ public enum PermissionDefault {
      */
     @Nullable
     public static PermissionDefault getByName(@NotNull String name) {
-        return lookup.get(name.toLowerCase(java.util.Locale.ENGLISH).replaceAll("[^a-z!]", ""));
+        return lookup.get(name.toLowerCase(Locale.ROOT).replaceAll("[^a-z!]", ""));
     }
 
     @Override

paper-api/src/main/java/org/bukkit/plugin/PluginDescriptionFile.java

@@ -9,6 +9,7 @@ import java.io.Writer;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.regex.Pattern;
@@ -1086,7 +1087,7 @@ public final class PluginDescriptionFile {
 
         if (map.get("load") != null) {
             try {
-                order = PluginLoadOrder.valueOf(((String) map.get("load")).toUpperCase(java.util.Locale.ENGLISH).replaceAll("\\W", ""));
+                order = PluginLoadOrder.valueOf(((String) map.get("load")).toUpperCase(Locale.ROOT).replaceAll("\\W", ""));
             } catch (ClassCastException ex) {
                 throw new InvalidDescriptionException(ex, "load is of wrong type");
             } catch (IllegalArgumentException ex) {

paper-api/src/main/java/org/bukkit/plugin/SimplePluginManager.java

@@ -18,6 +18,7 @@ import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.WeakHashMap;
@@ -698,7 +699,7 @@ public final class SimplePluginManager implements PluginManager {
     @Override
     @Nullable
     public Permission getPermission(@NotNull String name) {
-        return permissions.get(name.toLowerCase(java.util.Locale.ENGLISH));
+        return permissions.get(name.toLowerCase(Locale.ROOT));
     }
 
     @Override
@@ -708,7 +709,7 @@ public final class SimplePluginManager implements PluginManager {
 
     @Deprecated
     public void addPermission(@NotNull Permission perm, boolean dirty) {
-        String name = perm.getName().toLowerCase(java.util.Locale.ENGLISH);
+        String name = perm.getName().toLowerCase(Locale.ROOT);
 
         if (permissions.containsKey(name)) {
             throw new IllegalArgumentException("The permission " + name + " is already defined!");
@@ -731,12 +732,12 @@ public final class SimplePluginManager implements PluginManager {
 
     @Override
     public void removePermission(@NotNull String name) {
-        permissions.remove(name.toLowerCase(java.util.Locale.ENGLISH));
+        permissions.remove(name.toLowerCase(Locale.ROOT));
     }
 
     @Override
     public void recalculatePermissionDefaults(@NotNull Permission perm) {
-        if (perm != null && permissions.containsKey(perm.getName().toLowerCase(java.util.Locale.ENGLISH))) {
+        if (perm != null && permissions.containsKey(perm.getName().toLowerCase(Locale.ROOT))) {
             defaultPerms.get(true).remove(perm);
             defaultPerms.get(false).remove(perm);
 
@@ -775,7 +776,7 @@ public final class SimplePluginManager implements PluginManager {
 
     @Override
     public void subscribeToPermission(@NotNull String permission, @NotNull Permissible permissible) {
-        String name = permission.toLowerCase(java.util.Locale.ENGLISH);
+        String name = permission.toLowerCase(Locale.ROOT);
         Map<Permissible, Boolean> map = permSubs.get(name);
 
         if (map == null) {
@@ -788,7 +789,7 @@ public final class SimplePluginManager implements PluginManager {
 
     @Override
     public void unsubscribeFromPermission(@NotNull String permission, @NotNull Permissible permissible) {
-        String name = permission.toLowerCase(java.util.Locale.ENGLISH);
+        String name = permission.toLowerCase(Locale.ROOT);
         Map<Permissible, Boolean> map = permSubs.get(name);
 
         if (map != null) {
@@ -803,7 +804,7 @@ public final class SimplePluginManager implements PluginManager {
     @Override
     @NotNull
     public Set<Permissible> getPermissionSubscriptions(@NotNull String permission) {
-        String name = permission.toLowerCase(java.util.Locale.ENGLISH);
+        String name = permission.toLowerCase(Locale.ROOT);
         Map<Permissible, Boolean> map = permSubs.get(name);
 
         if (map == null) {

paper-api/src/main/java/org/bukkit/plugin/java/JavaPlugin.java

@@ -12,6 +12,7 @@ import java.io.Reader;
 import java.net.URL;
 import java.net.URLConnection;
 import java.util.List;
+import java.util.Locale;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import org.bukkit.Server;
@@ -309,11 +310,11 @@ public abstract class JavaPlugin extends PluginBase {
      */
     @Nullable
     public PluginCommand getCommand(@NotNull String name) {
-        String alias = name.toLowerCase(java.util.Locale.ENGLISH);
+        String alias = name.toLowerCase(Locale.ROOT);
         PluginCommand command = getServer().getPluginCommand(alias);
 
         if (command == null || command.getPlugin() != this) {
-            command = getServer().getPluginCommand(description.getName().toLowerCase(java.util.Locale.ENGLISH) + ":" + alias);
+            command = getServer().getPluginCommand(description.getName().toLowerCase(Locale.ROOT) + ":" + alias);
         }
 
         if (command != null && command.getPlugin() == this) {

paper-api/src/main/java/org/bukkit/potion/PotionEffectType.java

@@ -4,6 +4,7 @@ import com.google.common.base.Preconditions;
 import com.google.common.collect.BiMap;
 import com.google.common.collect.HashBiMap;
 import com.google.common.collect.Lists;
+import java.util.Locale;
 import org.bukkit.Color;
 import org.bukkit.Keyed;
 import org.bukkit.NamespacedKey;
@@ -348,7 +349,7 @@ public abstract class PotionEffectType implements Keyed, Translatable {
     @Deprecated
     public static PotionEffectType getByName(@NotNull String name) {
         Preconditions.checkArgument(name != null, "name cannot be null");
-        return Registry.EFFECT.get(NamespacedKey.fromString(name.toLowerCase(java.util.Locale.ENGLISH)));
+        return Registry.EFFECT.get(NamespacedKey.fromString(name.toLowerCase(Locale.ROOT)));
     }
 
     /**

paper-api/src/test/java/org/bukkit/ColorTest.java

@@ -3,6 +3,7 @@ package org.bukkit;
 import static org.bukkit.support.MatcherAssert.*;
 import static org.hamcrest.Matchers.*;
 import static org.junit.jupiter.api.Assertions.*;
+import java.util.Locale;
 import org.bukkit.configuration.file.YamlConfiguration;
 import org.junit.jupiter.api.Test;
 
@@ -31,7 +32,7 @@ public class ColorTest {
             this.r = r;
             this.g = g;
             this.b = b;
-            this.name = id + ":" + Integer.toHexString(argb).toUpperCase() + "_" + Integer.toHexString(rgb).toUpperCase() + "_" + Integer.toHexString(bgr).toUpperCase() + "-a" + Integer.toHexString(a).toUpperCase() + "-r" + Integer.toHexString(r).toUpperCase() + "-g" + Integer.toHexString(g).toUpperCase() + "-b" + Integer.toHexString(b).toUpperCase();
+            this.name = id + ":" + Integer.toHexString(argb).toUpperCase(Locale.ROOT) + "_" + Integer.toHexString(rgb).toUpperCase(Locale.ROOT) + "_" + Integer.toHexString(bgr).toUpperCase(Locale.ROOT) + "-a" + Integer.toHexString(a).toUpperCase(Locale.ROOT) + "-r" + Integer.toHexString(r).toUpperCase(Locale.ROOT) + "-g" + Integer.toHexString(g).toUpperCase(Locale.ROOT) + "-b" + Integer.toHexString(b).toUpperCase(Locale.ROOT);
         }
     }
 

paper-api/src/test/java/org/bukkit/MaterialTest.java

@@ -3,6 +3,7 @@ package org.bukkit;
 import static org.bukkit.support.MatcherAssert.*;
 import static org.hamcrest.Matchers.*;
 import static org.junit.jupiter.api.Assertions.*;
+import java.util.Locale;
 import org.bukkit.material.MaterialData;
 import org.junit.jupiter.api.Test;
 
@@ -66,7 +67,7 @@ public class MaterialTest {
     @Test
     public void matchMaterialByLowerCaseAndSpaces() {
         for (Material material : Material.values()) {
-            String name = material.toString().replaceAll("_", " ").toLowerCase(java.util.Locale.ENGLISH);
+            String name = material.toString().replaceAll("_", " ").toLowerCase(Locale.ROOT);
             assertThat(Material.matchMaterial(name), is(material));
         }
     }