Restrict user to give input up to 3 characters in javafx - javafx

Question

I am new to javaFx so please ignore my silly question here I want to validate (restrict) user to give 3 characters input (if user put more input, it should not allowed or after 3 characters, no latter should be visible) I found many solutions for validation but it does not restricting up to 3 characters as well as it little confusing to understand Here is my code.
public class editController {
#FXML
private TextField countrycode;
public void add(ActionEvent event) {
String ADD=countrycode.getText();
try {
if(ADD.isEmpty()){
Alert alert=new Alert(Alert.AlertType.ERROR);
alert.setHeaderText(null);
alert.setContentText("Please Fill All DATA");
alert.showAndWait();
return;
}
FXMLLoader loader =new FXMLLoader();
loader.load(getClass().getResource("/region/newCountry.fxml").openStream());

Answer 1

Validate using textProperty Listener like:
countrycode.textProperty().addListener(new ChangeListener<String>() {
public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
if (newValue.length() > 3) {
countrycode.setText(oldValue);
}
}
});
Or get a String length and check that like
int length = ADD.length();
if (length > 3) {
System.out.println("Please Enter Lessthen 3 character");
}

Answer 2

you have to #Override the replaceText(int,int,String) method of your textField this way:
#Override
public void replaceText(int start, int end, String text) {
if ("".equals(text)) { // handles delete
super.replaceText(start, end, text);
return;
}
if (getText().length() < 3) { // handles add and checks length.
super.replaceText(start, end, text);
}
}
This won't let you to insert more than 3 characters, but you can define any regexp and use instead of the second if condition.

Answer 3

The solution of #KeyurBhanderi is good enough until you are typing char by char. But when you try to paste from the clipboard a long text you will not see any changes in the text field. Surprise!
As alternative to avoid confusing set at least truncated string:
field.setText(newValue.substring(0, maxLimit));
In this case the end user will see a part of text and will quickly understand what is going on. Even better to show a popup window with a warning.