TextArea Demo

AsyncTextAreaUpdater.java

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import javafx.application.Application;
import javafx.beans.property.StringProperty;
import javafx.concurrent.Service;
import javafx.concurrent.Task;
import javafx.scene.Scene;
import javafx.scene.control.TextArea;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;

public class AsyncTextAreaUpdater extends Application {

    @Override
    public void start(Stage stage) throws Exception {
        AnchorPane root = new AnchorPane();
        TextArea area = new TextArea();
        root.getChildren().add(area);
        AnchorPane.setTopAnchor(area, 0.0);
        AnchorPane.setBottomAnchor(area, 0.0);
        AnchorPane.setLeftAnchor(area, 0.0);
        AnchorPane.setRightAnchor(area, 0.0);

        stage.setScene(new Scene(root, 400, 300));
        stage.show();

        Service<Void> service = new Service<Void>() {
            @Override
            protected Task<Void> createTask() {
                return new Task<Void>() {
                    @Override
                    protected Void call() throws Exception {
                        // ファイル名は適当にかえてください
                        Path path = Paths.get("text.txt");
                        List<String> lines = Files.readAllLines(path);

                        lines.forEach(line -> {
                            try {
                                updateMessage(line);
                                Thread.sleep(50l);
                            } catch (InterruptedException ex) {
                            }
                        });

                        return null;
                    }
                };
            }
        };

        service.start();
        
        // メッセージが変化したら、テキストエリアに反映させる
        service.messageProperty().addListener(o -> {
            StringProperty prop = (StringProperty)o;
            area.appendText(prop.get() + "\n");
        });
    }

    public static void main(String... args) {
        launch(args);
    }
}