Updated dependencies, activates PMD Plugin again: new version supports Java 21.

src/main/java/de/kneitzel/MainWindow.java

@@ -3,7 +3,6 @@ package de.kneitzel;
 import javafx.event.ActionEvent;
 import javafx.fxml.FXML;
 import javafx.fxml.Initializable;
-import javafx.scene.control.Button;
 import javafx.scene.control.TextField;
 
 import java.net.URL;
@@ -11,20 +10,24 @@ import java.util.ResourceBundle;
 
 public class MainWindow implements Initializable {
 
+
+    private int counter = 0;
+
     @FXML
     private TextField textField;
-    public Button button;
+
     @Override
-    public void initialize(URL url, ResourceBundle resourceBundle) {
-        if (button == null) {
-            textField.setText("Button is null");
-        } else {
-            textField.setText("Button is not null");
-        }
+    public void initialize(URL location, ResourceBundle resources) {
+        displayCounter();
+    }
+
+    private void displayCounter() {
+        textField.setText("Click counter: " + counter);
     }
 
     @FXML
     private void onButtonClick(ActionEvent actionEvent) {
-
+        counter++;
+        displayCounter();
     }
 }

src/main/resources/de/kneitzel/MainWindow.fxml

@@ -5,7 +5,7 @@
 
 <AnchorPane prefHeight="127.0" prefWidth="209.0" xmlns="http://javafx.com/javafx/17.0.2-ea" xmlns:fx="http://javafx.com/fxml/1" fx:controller="de.kneitzel.MainWindow">
    <children>
-      <Button fx:id="button" layoutX="44.0" layoutY="70.0" mnemonicParsing="false" onAction="#onButtonClick" text="Button" />
+      <Button fx:id="button" layoutX="44.0" layoutY="70.0" mnemonicParsing="false" onAction="#onButtonClick" text="Click Me" />
       <TextField fx:id="textField" layoutX="14.0" layoutY="24.0" />
    </children>
 </AnchorPane>