Numeral TextField in JavaFX

numeralField.java

/** numberfield can be any input field, like spinner, textfield, etc.
/* here numberfield is textfield
/* I commented the necessary imports.
**/

//import java.util.function.UnaryOperator;
//import javafx.scene.control.TextFormatter;

@FXML
private Spinner<Double> balanceField;
//the declaration is out of methods. but the UnaryOperator is in a method like initialize.

public void initialize(URL url, ResourceBundle rb){
	UnaryOperator<TextFormatter.Change> filter = change -> {
            	String newText = change.getControlNewText();
            	if(newText.matches("([0-9])*[.]([0-9])*"))
                		return change;  //if the regular expression matches the input value.
            	return null;
        	};
            //setting textformatter to the numberfield
            balanceField.getEditor().setTextFormatter(new TextFormatter<>(filter));
}

the ([0-9])*[.]([0-9])* is a regular expression for accepting double numbers.