How do you validate a phone number in Java with a do/while?

Question

I am trying to validate a phone number using Java. How can I ensure that the string is also the correct length (10 digits).

do{
    System.out.println("Please provide the phone number starting with area code: ");
    this.phone = input.nextLine();
} while (!phone.matches("[0-9]"));

If you're going to use a regex, why not: `while (!phone.matches("\d{10}");` — dave, Oct 26 '17 at 01:17
https://docs.oracle.com/javase/tutorial/essential/regex/quant.html — Tom, Oct 26 '17 at 01:18
@dave generally correct, but `\d` is wrong. Should be `\\d`. — Tom, Oct 26 '17 at 01:23
@dave and that's why you need to escape the first backslash. — Tom, Oct 26 '17 at 01:28
@dave backslash is a Java escape character in a `String`. `"\\d{10}"` is the valid one. — CallMeLaNN, Oct 26 '17 at 07:36

Joshua K · Answer 1 · 2017-10-26T01:23:23.787

0

you have to change your regular expression to match exactly 10 digits.

do{
    System.out.println("Please provide the phone number starting with area code: ");
    this.phone = input.nextLine();
}while (!phone.matches("[0-9]{10}"));

One thing: I'm not sure if this type of validation is good. What if the user enters his phone number with a leading plus sign or something like that? Whitespaces as seperator?

edited Oct 26 '17 at 01:23

answered Oct 26 '17 at 01:11

Joshua K

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How do you validate a phone number in Java with a do/while?

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