SPIGOT-2540: Add nullability annotations to entire Bukkit API

By: Darkyenus <darkyenus@gmail.com>

paper-api/src/main/java/org/bukkit/conversations/Conversation.java

@@ -1,6 +1,8 @@
 package org.bukkit.conversations;
 
 import org.bukkit.plugin.Plugin;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -51,7 +53,7 @@ public class Conversation {
      * @param forWhom The entity for whom this conversation is mediating.
      * @param firstPrompt The first prompt in the conversation graph.
      */
-    public Conversation(Plugin plugin, Conversable forWhom, Prompt firstPrompt) {
+    public Conversation(@Nullable Plugin plugin, @NotNull Conversable forWhom, @Nullable Prompt firstPrompt) {
         this(plugin, forWhom, firstPrompt, new HashMap<Object, Object>());
     }
 
@@ -64,7 +66,7 @@ public class Conversation {
      * @param initialSessionData Any initial values to put in the conversation
      *     context sessionData map.
      */
-    public Conversation(Plugin plugin, Conversable forWhom, Prompt firstPrompt, Map<Object, Object> initialSessionData) {
+    public Conversation(@Nullable Plugin plugin, @NotNull Conversable forWhom, @Nullable Prompt firstPrompt, @NotNull Map<Object, Object> initialSessionData) {
         this.firstPrompt = firstPrompt;
         this.context = new ConversationContext(plugin, forWhom, initialSessionData);
         this.modal = true;
@@ -79,6 +81,7 @@ public class Conversation {
      *
      * @return The entity.
      */
+    @NotNull
     public Conversable getForWhom() {
         return context.getForWhom();
     }
@@ -133,6 +136,7 @@ public class Conversation {
      *
      * @return The ConversationPrefix in use.
      */
+    @NotNull
     public ConversationPrefix getPrefix() {
         return prefix;
     }
@@ -143,7 +147,7 @@ public class Conversation {
      *
      * @param prefix The ConversationPrefix to use.
      */
-    void setPrefix(ConversationPrefix prefix) {
+    void setPrefix(@NotNull ConversationPrefix prefix) {
         this.prefix = prefix;
     }
 
@@ -152,7 +156,7 @@ public class Conversation {
      *
      * @param canceller The {@link ConversationCanceller} to add.
      */
-    void addConversationCanceller(ConversationCanceller canceller) {
+    void addConversationCanceller(@NotNull ConversationCanceller canceller) {
         canceller.setConversation(this);
         this.cancellers.add(canceller);
     }
@@ -162,6 +166,7 @@ public class Conversation {
      *
      * @return The list.
      */
+    @NotNull
     public List<ConversationCanceller> getCancellers() {
         return cancellers;
     }
@@ -171,6 +176,7 @@ public class Conversation {
      *
      * @return The ConversationContext.
      */
+    @NotNull
     public ConversationContext getContext() {
         return context;
     }
@@ -192,6 +198,7 @@ public class Conversation {
      *
      * @return The current state of the conversation.
      */
+    @NotNull
     public ConversationState getState() {
         if (currentPrompt != null) {
             return ConversationState.STARTED;
@@ -208,7 +215,7 @@ public class Conversation {
      *
      * @param input The user's chat text.
      */
-    public void acceptInput(String input) {
+    public void acceptInput(@NotNull String input) {
         if (currentPrompt != null) {
 
             // Echo the user's input
@@ -235,7 +242,7 @@ public class Conversation {
      *
      * @param listener The listener to add.
      */
-    public synchronized void addConversationAbandonedListener(ConversationAbandonedListener listener) {
+    public synchronized void addConversationAbandonedListener(@NotNull ConversationAbandonedListener listener) {
         abandonedListeners.add(listener);
     }
 
@@ -244,7 +251,7 @@ public class Conversation {
      *
      * @param listener The listener to remove.
      */
-    public synchronized void removeConversationAbandonedListener(ConversationAbandonedListener listener) {
+    public synchronized void removeConversationAbandonedListener(@NotNull ConversationAbandonedListener listener) {
         abandonedListeners.remove(listener);
     }
 
@@ -262,7 +269,7 @@ public class Conversation {
      *
      * @param details Details about why the conversation was abandoned
      */
-    public synchronized void abandon(ConversationAbandonedEvent details) {
+    public synchronized void abandon(@NotNull ConversationAbandonedEvent details) {
         if (!abandoned) {
             abandoned = true;
             currentPrompt = null;