SPIGOT-2540: Add nullability annotations to entire Bukkit API

By: Darkyenus <darkyenus@gmail.com>

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

@@ -1,5 +1,8 @@
 package org.bukkit.permissions;
 
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
 import java.util.HashMap;
 import java.util.Map;
 
@@ -15,7 +18,7 @@ public enum PermissionDefault {
     private final String[] names;
     private final static Map<String, PermissionDefault> lookup = new HashMap<String, PermissionDefault>();
 
-    private PermissionDefault(String... names) {
+    private PermissionDefault(@NotNull String... names) {
         this.names = names;
     }
 
@@ -47,7 +50,8 @@ public enum PermissionDefault {
      * @param name Name of the default
      * @return Specified value, or null if not found
      */
-    public static PermissionDefault getByName(String name) {
+    @Nullable
+    public static PermissionDefault getByName(@NotNull String name) {
         return lookup.get(name.toLowerCase(java.util.Locale.ENGLISH).replaceAll("[^a-z!]", ""));
     }