printing input from JavaFX TextArea to console gives errors

Question

I am trying to print the input from a user in a TextArea to the console.

//controller
    private void btnClick(ActionEvent event) {
        System.out.println(input.getText());
    }


//fxml
...
   <left>
      <Button id="booton" fx:id="booton" mnemonicParsing="false" onAction="#btnClick" text="Button" BorderPane.alignment="CENTER" />
   </left>
   <right>
      <TextArea id="input" prefHeight="200.0" prefWidth="200.0" promptText="give me input" BorderPane.alignment="CENTER" />
   </right>
</BorderPane>

It gives me this error when running along with alot more:

Caused by: java.lang.NullPointerException: Cannot invoke "javafx.scene.control.TextArea.getText()" because "this.input" is null at sample.Controller.btnClick(Controller.java:31)