No reason to use the SAME CODE in three different clases.

src/main/java/com/gmail/nossr50/party/PartyManager.java

@@ -21,6 +21,21 @@ public final class PartyManager {
 
     private PartyManager() {}
 
+    public static boolean changeOrJoinParty(McMMOPlayer mcMMOPlayer, Player player, Party oldParty, Party newParty) {
+        if (mcMMOPlayer.inParty()) {
+            if (!handlePartyChangeEvent(player, oldParty.getName(), newParty.getName(), EventReason.CHANGED_PARTIES)) {
+                return false;
+            }
+
+            removeFromParty(player.getName(), oldParty);
+        }
+        else if (!handlePartyChangeEvent(player, null, newParty.getName(), EventReason.JOINED_PARTY)) {
+            return false;
+        }
+
+        return true;
+    }
+
     /**
      * Check if two players are in the same party.
      *

src/main/java/com/gmail/nossr50/party/commands/PartyAcceptCommand.java

@@ -6,9 +6,7 @@ import org.bukkit.command.CommandSender;
 import org.bukkit.entity.Player;
 
 import com.gmail.nossr50.datatypes.McMMOPlayer;
-import com.gmail.nossr50.events.party.McMMOPartyChangeEvent.EventReason;
 import com.gmail.nossr50.locale.LocaleLoader;
-import com.gmail.nossr50.party.Party;
 import com.gmail.nossr50.party.PartyManager;
 import com.gmail.nossr50.util.Permissions;
 import com.gmail.nossr50.util.Users;
@@ -16,7 +14,6 @@ import com.gmail.nossr50.util.Users;
 public class PartyAcceptCommand implements CommandExecutor {
     private McMMOPlayer mcMMOPlayer;
     private Player player;
-    private Party playerParty;
 
     @Override
     public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
@@ -35,17 +32,9 @@ public class PartyAcceptCommand implements CommandExecutor {
                 return true;
             }
 
-            // Changing parties
-            if (mcMMOPlayer.inParty()) {
-                playerParty = mcMMOPlayer.getParty();
-
-                if (!PartyManager.handlePartyChangeEvent(player, playerParty.getName(), mcMMOPlayer.getPartyInvite().getName(), EventReason.CHANGED_PARTIES)) {
-                    return true;
-                }
 
-                PartyManager.removeFromParty(player.getName(), playerParty);
-            }
-            else if (!PartyManager.handlePartyChangeEvent(player, null, mcMMOPlayer.getPartyInvite().getName(), EventReason.JOINED_PARTY)) {
+            // Changing parties
+            if (!PartyManager.changeOrJoinParty(mcMMOPlayer, player, mcMMOPlayer.getParty(), mcMMOPlayer.getPartyInvite())) {
                 return true;
             }
 

src/main/java/com/gmail/nossr50/party/commands/PartyCreateCommand.java

@@ -6,7 +6,6 @@ import org.bukkit.command.CommandSender;
 import org.bukkit.entity.Player;
 
 import com.gmail.nossr50.datatypes.McMMOPlayer;
-import com.gmail.nossr50.events.party.McMMOPartyChangeEvent.EventReason;
 import com.gmail.nossr50.locale.LocaleLoader;
 import com.gmail.nossr50.party.Party;
 import com.gmail.nossr50.party.PartyManager;
@@ -16,7 +15,6 @@ import com.gmail.nossr50.util.Users;
 public class PartyCreateCommand implements CommandExecutor {
     private McMMOPlayer mcMMOPlayer;
     private Player player;
-    private Party playerParty;
 
     @Override
     public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
@@ -40,15 +38,7 @@ public class PartyCreateCommand implements CommandExecutor {
             mcMMOPlayer = Users.getPlayer(player);
 
             // Changing parties
-            if (mcMMOPlayer.inParty()) {
-                playerParty = mcMMOPlayer.getParty();
-                if (!PartyManager.handlePartyChangeEvent(player, playerParty.getName(), args[1], EventReason.CHANGED_PARTIES)) {
-                    return true;
-                }
-
-                PartyManager.removeFromParty(player.getName(), playerParty);
-            }
-            else if (!PartyManager.handlePartyChangeEvent(player, null, args[1], EventReason.JOINED_PARTY)) {
+            if (!PartyManager.changeOrJoinParty(mcMMOPlayer, player, mcMMOPlayer.getParty(), newParty)) {
                 return true;
             }
 

src/main/java/com/gmail/nossr50/party/commands/PartyJoinCommand.java

@@ -7,7 +7,6 @@ import org.bukkit.entity.Player;
 
 import com.gmail.nossr50.datatypes.McMMOPlayer;
 import com.gmail.nossr50.datatypes.PlayerProfile;
-import com.gmail.nossr50.events.party.McMMOPartyChangeEvent.EventReason;
 import com.gmail.nossr50.locale.LocaleLoader;
 import com.gmail.nossr50.party.Party;
 import com.gmail.nossr50.party.PartyManager;
@@ -46,18 +45,11 @@ public class PartyJoinCommand implements CommandExecutor {
             }
 
             // Changing parties
-            if (mcMMOPlayer.inParty()) {
-                if (!PartyManager.handlePartyChangeEvent(player, playerParty.getName(), targetParty.getName(), EventReason.CHANGED_PARTIES)) {
-                    return true;
-                }
-
-                PartyManager.removeFromParty(player.getName(), playerParty);
-            }
-            else if (!PartyManager.handlePartyChangeEvent(player, null, targetParty.getName(), EventReason.JOINED_PARTY)) {
+            if (!PartyManager.changeOrJoinParty(mcMMOPlayer, player, playerParty, targetParty)) {
                 return true;
             }
 
-            PartyManager.joinParty(player, mcMMOPlayer, targetParty.getName(), password);
+            PartyManager.joinParty(player, mcMMOPlayer, playerParty.getName(), password);
             return true;
 
         default: