@@ -42,7 +42,7 @@ public class StepRepresentationTextBox extends StepRepresentationMessage {
 
         textField = new TextField();
         textField.textProperty().addListener((observable, oldValue, newValue) -> {
-            if (newValue.trim().equals("")) {
+            if ("".equals(newValue.trim())) {
                 setNextButtonEnabled(false);
             } else {
                 setNextButtonEnabled(true);
/*
 * Copyright (C) 2015-2017 PÂRIS Quentin
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

package org.phoenicis.javafx.views.scriptui;

import org.phoenicis.scripts.ui.Message;
import javafx.scene.control.TextField;

public class StepRepresentationTextBox extends StepRepresentationMessage {
    private final String defaultValue;
    private final Message<String> messageWaitingForResponse;
    private TextField textField;

    public StepRepresentationTextBox(SetupUiJavaFXImplementation parent, Message<String> messageWaitingForResponse,
            String textToShow, String defaultValue) {
        super(parent, messageWaitingForResponse, textToShow);
        this.messageWaitingForResponse = messageWaitingForResponse;

        this.defaultValue = defaultValue;
    }

    @Override
    protected void drawStepContent() {
        super.drawStepContent();

        setNextButtonEnabled(false);

        textField = new TextField();
        textField.textProperty().addListener((observable, oldValue, newValue) -> {
            if (newValue.trim().equals("")) {
                setNextButtonEnabled(false);
            } else {
                setNextButtonEnabled(true);
            }
        });
        textField.setText(defaultValue);
        textField.setLayoutX(10);
        textField.setLayoutY(40);

        this.addToContentPane(textField);
    }

    @Override
    protected void setStepEvents() {
        this.setNextButtonAction(event -> messageWaitingForResponse.send(textField.getText()));
    }

}

I think `newValue.trim().isEmpty()` would be even better here