SPIGOT-2540: Add nullability annotations to entire Bukkit API

By: Darkyenus <darkyenus@gmail.com>

paper-api/src/main/java/org/bukkit/map/MapFont.java

@@ -2,6 +2,8 @@ package org.bukkit.map;
 
 import java.util.HashMap;
 import org.bukkit.ChatColor;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * Represents a bitmap font drawable to a map.
@@ -19,7 +21,7 @@ public class MapFont {
      * @param sprite The CharacterSprite to set.
      * @throws IllegalStateException if this font is static.
      */
-    public void setChar(char ch, CharacterSprite sprite) {
+    public void setChar(char ch, @NotNull CharacterSprite sprite) {
         if (!malleable) {
             throw new IllegalStateException("this font is not malleable");
         }
@@ -37,6 +39,7 @@ public class MapFont {
      * @return The CharacterSprite associated with the character, or null if
      *     there is none.
      */
+    @Nullable
     public CharacterSprite getChar(char ch) {
         return chars.get(ch);
     }
@@ -48,7 +51,7 @@ public class MapFont {
      * @param text The text.
      * @return The width in pixels.
      */
-    public int getWidth(String text) {
+    public int getWidth(@NotNull String text) {
         if (!isValid(text)) {
             throw new IllegalArgumentException("text contains invalid characters");
         }
@@ -84,7 +87,7 @@ public class MapFont {
      * @return True if the string contains only defined characters, false
      *     otherwise.
      */
-    public boolean isValid(String text) {
+    public boolean isValid(@NotNull String text) {
         for (int i = 0; i < text.length(); ++i) {
             char ch = text.charAt(i);
             if (ch == ChatColor.COLOR_CHAR || ch == '\n') continue;
@@ -102,7 +105,7 @@ public class MapFont {
         private final int height;
         private final boolean[] data;
 
-        public CharacterSprite(int width, int height, boolean[] data) {
+        public CharacterSprite(int width, int height, @NotNull boolean[] data) {
             this.width = width;
             this.height = height;
             this.data = data;