Javafx Textfield: Accept only digits of length 8 or 11 ( phone numbers)

Question

Working on a project with javafx and I'm having a minor hitch. I want my textfield to accept only digits, 8 or 11 in length. Here's my code:

if(!txtPhone.getText().matches(.....) && (txtPhone.getText().length != 8 || txtPhone.getText(). length != 11){
System.out.print("Please enter a valid phone number");
}

You want the error message to be displayed if one of the criterions is satisfied, right? Currently the expression in the brackets always evaluates to `true` (after fixing the syntax errors): The text length is always different to 8, 11 or both. This makes the expression logically equivalent to `!txtPhone.getText().matches(.....)`. You probably intended to use `String text = texttPhone.getText(); if (!(((text.length() == 11) || (text.length() == 8)) && text.matches("\\d*")))` (Note that I reordered the conditions a bit, since comparing the string lenght takes less time than matching the regex.) — fabian, Nov 18 '19 at 17:17
Using de morgan you could write the condition in the above comment to `!text.matches("\\d*") || (text.length() != 8 && text.length() != 11)`, i.e. it's an error, if the text doesn't contain only digits or if the text lenght is different to both allowed lenghts. — fabian, Nov 18 '19 at 17:20

mr mcwolf · Answer 1 · 2019-11-18T11:14:47.970

1

The task involves two stages:

You must first create a text box that accepts digits only (up to 11 maximum).
Second, you have to customize the user input according to your criteria (8 or 11 digits)

TextFormatter is used to solve the problem. A UnaryOperator must be passed to it to filter user input only by numbers and StringConverter to validate user input.

This is an example implementation:

UnaryOperator<TextFormatter.Change> filter = change -> {
    if(change.getControlNewText().matches("\\d{0,11}")) {
        return change;
    }

    return null;
};

StringConverter<String> converter = new StringConverter<String>() {
    @Override
    public String toString(String s) {
        if(s == null || s.isBlank()) return "";

        if(s.matches("\\d{8}|\\d{11}")) {
            return s;
        }

        return "";
    }

    @Override
    public String fromString(String s) {
        if(s == null || s.isBlank()) return "";

        if(s.matches("\\d{8}|\\d{11}")) {
            return s;
        }

        throw new RuntimeException("Converter error");
    }
};

textField.setTextFormatter(new TextFormatter<>(converter, null, filter));

edited Nov 18 '19 at 11:14

answered Nov 18 '19 at 11:04

mr mcwolf

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Thanks @mr mcwolf. How do I fit these into the if statement above, in a line of code? – John Omage Nov 18 '19 at 22:05
@JohnOmage, the `if` operator above is practically useless. It simply prints text in the console. And this in the context of the GUI only makes sense as a debug output. If so, paste tracking messages into the body of `StringConverter::fromString`. – mr mcwolf Nov 19 '19 at 07:15
It seems more likely that you want to notify the user that he or she did not enter the phone number before proceeding. Therefore, there are several possible approaches: disable the OK button, disable the dialog closing with the corresponding message, or simply show a notification (icon, text ...) that the field is blank. How exactly to do this is impossible to say since there is no additional information. – mr mcwolf Nov 19 '19 at 07:15

score 1 · Accepted Answer · answered Nov 19 '19 at 04:52

Regular Expression can be used to create custom validations.

if (txtPhone.getText().matches("\\d{8}|\\d{11}") {

    System.out.println("Its Valid Number");
    //return true;
}else {

    System.out.println("Invalid Input..!");
    //return false;
}

You can learn and check about Regular Expressions Here

Javafx Textfield: Accept only digits of length 8 or 11 ( phone numbers)

2 Answers2