Trying to use regex

Question about the task

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I've tried testing my code with the examples provided in the conditions and it doesn't work. I'm not sure that I've used the escape characters properly. Also, line 16

if (temp.length() != 10) return false;

has a warning "Condition is always true", and I'm not sure why

The checkPhoneNumber method should check whether the phoneNumber argument is a valid phone number.

Verification criteria:
1) if the number starts with '+', then it must contain 12 digits
2) if the number starts with a digit or opening parenthesis, then it must contain 10 digits
3) the number may contain 0-2 non-consecutive '-' characters
4) the number may contain 1 pair of matching parentheses, which must be to the left of the '-' characters
5) the parentheses must contain exactly 3 digits
6) the number cannot contain letters
7) the number must end with a digit

Here are some examples:

+380501234567 - true
+38(050)1234567 - true
+38050123-45-67 - true
050123-4567 - true
+38)050(1234567 - false
+38(050)1-23-45-6-7 - false
050xxx4567 - false
050123456 - false
(0)501234567 - false

Requirements:

The checkPhoneNumber method should return a boolean.
The checkPhoneNumber method must be public.
The checkPhoneNumber method must have one String parameter.
The checkPhoneNumber method must correctly check the validity of the phone number passed as an argument.

package com.codegym.task.task22.task2212; /* Phone number verification */ public class Solution { public static boolean checkPhoneNumber(String phoneNumber) { //check amount of digits String temp = phoneNumber.replaceAll("[^0-9]", ""); if (phoneNumber.startsWith("+")) if (temp.length() != 12) return false; else if (temp.length() != 10) return false; //check amount of - temp = phoneNumber.replaceAll("-", ""); if (temp.length() > 2) return false; //check placement of - if (phoneNumber.matches("\\.*--\\.*")) return false; //check amount of () temp = phoneNumber.replaceAll("\\(", ""); if (temp.length() > 1) return false; //check placement of () if (phoneNumber.contains("(") && !phoneNumber.matches("\\.*\\(\\d{3}\\)\\.*")) return false; if (phoneNumber.matches("\\.*-\\.*\\(\\.*")) return false; //check if contains letters and ends with digit if (phoneNumber.contains("[a-zA-Z") || !phoneNumber.endsWith("\\d")) return false; return true; } public static void main(String[] args) { boolean test = checkPhoneNumber("+38(050)1234567"); System.out.println(test); } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

14 February 2021, 16:47

useful

#1 you have managed to confuse the computer with lines 13-16. I understand what your intentions are, as your indentation clearly points this out, however this is what the computer sees (and the way it is processing it):

if (phoneNumber.startsWith("+"))
    if (temp.length() != 12) return false;
    else if (temp.length() != 10) return false;

In this case you should add brackets to ensure the computer processes exactly as you intend:

if (phoneNumber.startsWith("+")) {
    if (temp.length() != 12) return false;
}else if (temp.length() != 10) return false;

#2 The escape sequences are being used incorrectly. This is causing it to not be able to find matches as intended. You don't need to escape period chars '.' unless you intend to check for a period. In a regex the peroid char means "any character". Remove the escapes from these on lines 22, 28, and 29. #3a Line 19 and line 20 are logically incorrect: Remove all "-" and then check if the String is longer than 2. Unless the String was "----------" this result will most likely be longer than 2 #3b Lines 25 and 26 have the same error in logic #4 there is a typo on line 32, a missing closing bracket. #5 And finally, line 32: The endsWith() method does not accept a regex. This is checking that the String ends with exactly what you ask for, in this case "\\d". This would only be true if the String were something line this: "123324\\d".

Anthony Chalk

Level 30 , London, United Kingdom

15 February 2021, 20:34

My code is now:

public static boolean checkPhoneNumber(String phoneNumber) {

    //check amount of digits
    String temp = phoneNumber.replaceAll("[^0-9]", "");
    if (phoneNumber.startsWith("+")) {
        if (temp.length() != 12) return false;
    }
    else {
        if (temp.length() != 10) return false;
    }

    //check amount of -
    temp = phoneNumber.replaceAll("[^-]", "");
    if (temp.length() > 2) return false;
    //check placement of -
    if (phoneNumber.matches(".*--.*")) return false;

    //check amount of ()
    temp = phoneNumber.replaceAll("[^\\(]", "");
    if (temp.length() > 1) return false;
    //check placement of ()
    if (phoneNumber.contains("(") && !phoneNumber.matches(".*\\(\\d{3}\\).*")) return false;
    if (phoneNumber.matches(".*-.*\\(.*")) return false;

    //check if contains letters and ends with digit
    if (phoneNumber.contains("[a-zA-Z") ||
            !Character.isDigit(phoneNumber.charAt(phoneNumber.length()-1))) return false;

    return true;
}

it gives the right result for all the examples given in the test bust still fails

Guadalupe Gagnon

Level 37 , Tampa, United States

15 February 2021, 21:26

solution

One additional. The first two statements: 1) if the number starts with '+', then it must contain 12 digits 2) if the number starts with a digit or opening parenthesis, then it must contain 10 digits say that the phone number must start with either a '+', a digit, or a '('. If you test your code starting with the only other char that could exist in a phone number, the dash, it is returning true (when there are 10 numbers). So this one should be false: "-0123456789"

Anthony Chalk

Level 30 , London, United Kingdom

15 February 2021, 22:05

Thanks very much. I also needed to check if it was null, but why isn't that case already handled by:

if (temp.length() != 10) return false;

matemate123

Level 50 , Kraków, Poland

22 March 2023, 05:37

Really nice using regex man