Implemented good suggestion by @delvh regarding performance increase

src/main/java/envoy/client/data/Chat.java

@@ -29,6 +29,8 @@ public class Chat implements Serializable {
 	protected final Contact			recipient;
 	protected final List<Message>	messages	= new ArrayList<>();
 
+	protected int unreadAmount;
+
 	private static final long serialVersionUID = 1L;
 
 	/**
@@ -87,6 +89,7 @@ public class Chat implements Serializable {
 				writeProxy.writeMessageStatusChange(new MessageStatusChange(m));
 			}
 		}
+		unreadAmount = 0;
 	}
 
 	/**
@@ -111,14 +114,9 @@ public class Chat implements Serializable {
 		messages.add(0, message);
 	}
 
-	public int getUnreadAmount() {
-		int unreadMessagesAmount = 0;
-		for (int i = messages.size() - 1; i >= 0; i--) {
-			if (messages.get(i).getSenderID() == recipient.getID() && messages.get(i).getStatus() == MessageStatus.RECEIVED) unreadMessagesAmount++;
-			else break;
-		}
-		return unreadMessagesAmount;
-	}
+	public void incrementUnreadAmount() { unreadAmount++; }
+
+	public int getUnreadAmount() { return unreadAmount; }
 
 	/**
 	 * @return all messages in the current chat

src/main/java/envoy/client/data/GroupChat.java

@@ -37,16 +37,6 @@ public class GroupChat extends Chat {
 		this.sender = sender;
 	}
 
-	@Override
-	public int getUnreadAmount() {
-		int unreadMessagesAmount = 0;
-		for (int i = messages.size() - 1; i >= 0; i--) {
-			if (messages.get(i).getSenderID() != sender.getID() && messages.get(i).getStatus() == MessageStatus.RECEIVED) unreadMessagesAmount++;
-			else break;
-		}
-		return unreadMessagesAmount;
-	}
-
 	@Override
 	public void read(WriteProxy writeProxy) throws IOException {
 		for (int i = messages.size() - 1; i >= 0; --i) {
@@ -60,5 +50,6 @@ public class GroupChat extends Chat {
 				}
 			}
 		}
+		super.unreadAmount = 0;
 	}
 }

src/main/java/envoy/client/ui/controller/ChatScene.java

@@ -134,7 +134,7 @@ public final class ChatScene implements Restorable {
 						logger.log(Level.WARNING, "Could not read current chat: ", e1);
 					}
 					Platform.runLater(() -> { messageList.refresh(); scrollToMessageListEnd(); });
-				}
+				} else chat.incrementUnreadAmount();
 				// Moving chat with most recent unreadMessages to the top
 				Platform.runLater(() -> {
 					userList.getItems().remove(chat);