How get an event when text in a TextField changes? JavaFX

Register a listener with the TextFields textProperty:

textField.textProperty().addListener((obs, oldText, newText) -> {
    System.out.println("Text changed from "+oldText+" to "+newText);
    // ...
});

Or Use ChangeListener interface.

textField.textProperty().addListener(new ChangeListener<String>() {
    @Override
    public void changed(ObservableValue<? extends String> observable,
            String oldValue, String newValue) {

        System.out.println(" Text Changed to  " + newValue + ")\n");
    }
});