SPIGOT-2540: Add nullability annotations to entire Bukkit API

By: Darkyenus <darkyenus@gmail.com>

paper-api/src/main/java/org/bukkit/block/banner/Pattern.java

@@ -6,6 +6,7 @@ import java.util.NoSuchElementException;
 import org.bukkit.DyeColor;
 import org.bukkit.configuration.serialization.ConfigurationSerializable;
 import org.bukkit.configuration.serialization.SerializableAs;
+import org.jetbrains.annotations.NotNull;
 
 @SerializableAs("Pattern")
 public class Pattern implements ConfigurationSerializable {
@@ -23,7 +24,7 @@ public class Pattern implements ConfigurationSerializable {
      * @param color   the pattern color
      * @param pattern the pattern type
      */
-    public Pattern(DyeColor color, PatternType pattern) {
+    public Pattern(@NotNull DyeColor color, @NotNull PatternType pattern) {
         this.color = color;
         this.pattern = pattern;
     }
@@ -33,12 +34,12 @@ public class Pattern implements ConfigurationSerializable {
      *
      * @param map the map to deserialize from
      */
-    public Pattern(Map<String, Object> map) {
+    public Pattern(@NotNull Map<String, Object> map) {
         color = DyeColor.legacyValueOf(getString(map, COLOR));
         pattern = PatternType.getByIdentifier(getString(map, PATTERN));
     }
 
-    private static String getString(Map<?, ?> map, Object key) {
+    private static String getString(@NotNull Map<?, ?> map, @NotNull Object key) {
         Object str = map.get(key);
         if (str instanceof String) {
             return (String) str;
@@ -46,6 +47,7 @@ public class Pattern implements ConfigurationSerializable {
         throw new NoSuchElementException(map + " does not contain " + key);
     }
 
+    @NotNull
     @Override
     public Map<String, Object> serialize() {
         return ImmutableMap.<String, Object>of(
@@ -59,6 +61,7 @@ public class Pattern implements ConfigurationSerializable {
      *
      * @return the color of the pattern
      */
+    @NotNull
     public DyeColor getColor() {
         return color;
     }
@@ -68,6 +71,7 @@ public class Pattern implements ConfigurationSerializable {
      *
      * @return the pattern type
      */
+    @NotNull
     public PatternType getPattern() {
         return pattern;
     }

paper-api/src/main/java/org/bukkit/block/banner/PatternType.java

@@ -1,5 +1,9 @@
 package org.bukkit.block.banner;
 
+import org.jetbrains.annotations.Contract;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
 import java.util.HashMap;
 import java.util.Map;
 
@@ -53,7 +57,7 @@ public enum PatternType {
         }
     }
 
-    private PatternType(String key) {
+    private PatternType(@NotNull String key) {
         this.identifier = key;
     }
 
@@ -63,6 +67,7 @@ public enum PatternType {
      *
      * @return the pattern's identifier
      */
+    @NotNull
     public String getIdentifier() {
         return identifier;
     }
@@ -74,7 +79,9 @@ public enum PatternType {
      * @param identifier the identifier
      * @return the matched pattern type or null
      */
-    public static PatternType getByIdentifier(String identifier) {
+    @Contract("null -> null")
+    @Nullable
+    public static PatternType getByIdentifier(@Nullable String identifier) {
         return byString.get(identifier);
     }
 }