Java generates REGEX for valid phone numbers
Another alternative is to let Java generate a REGEX that macthes all variations of phone numbers read from a list. This means that the list called validPhoneNumbersFormat, seen below in code context, is deciding which phone number format is valid.
Note: This type of algorithm would work for any language handling regular expressions.
Code snippet that generates the REGEX:
Set<String> regexSet = uniqueValidPhoneNumbersFormats.stream()
        .map(s -> s.replaceAll("\\+", "\\\\+"))
        .map(s -> s.replaceAll("\\d", "\\\\d"))
        .map(s -> s.replaceAll("\\.", "\\\\."))
        .map(s -> s.replaceAll("([\\(\\)])", "\\\\$1"))
        .collect(Collectors.toSet());
String regex = String.join("|", regexSet);
Code snippet in context:
public class TestBench {
    public static void main(String[] args) {
        List<String> validPhoneNumbersFormat = Arrays.asList(
                "1-234-567-8901",
                "1-234-567-8901 x1234",
                "1-234-567-8901 ext1234",
                "1 (234) 567-8901",
                "1.234.567.8901",
                "1/234/567/8901",
                "12345678901",
                "+12345678901",
                "(234) 567-8901 ext. 123",
                "+1 234-567-8901 ext. 123",
                "1 (234) 567-8901 ext. 123",
                "00 1 234-567-8901 ext. 123",
                "+210-998-234-01234",
                "210-998-234-01234",
                "+21099823401234",
                "+210-(998)-(234)-(01234)",
                "(+351) 282 43 50 50",
                "90191919908",
                "555-8909",
                "001 6867684",
                "001 6867684x1",
                "1 (234) 567-8901",
                "1-234-567-8901 x1234",
                "1-234-567-8901 ext1234",
                "1-234 567.89/01 ext.1234",
                "1(234)5678901x1234",
                "(123)8575973",
                "(0055)(123)8575973"
        );
        Set<String> uniqueValidPhoneNumbersFormats = new LinkedHashSet<>(validPhoneNumbersFormat);
        List<String> invalidPhoneNumbers = Arrays.asList(
                "+210-99A-234-01234",       // FAIL
                "+210-999-234-0\"\"234",    // FAIL
                "+210-999-234-02;4",        // FAIL
                "-210+998-234-01234",       // FAIL
                "+210-998)-(234-(01234"     // FAIL
        );
        List<String> invalidAndValidPhoneNumbers = new ArrayList<>();
        invalidAndValidPhoneNumbers.addAll(invalidPhoneNumbers);
        invalidAndValidPhoneNumbers.addAll(uniqueValidPhoneNumbersFormats);
        Set<String> regexSet = uniqueValidPhoneNumbersFormats.stream()
                .map(s -> s.replaceAll("\\+", "\\\\+"))
                .map(s -> s.replaceAll("\\d", "\\\\d"))
                .map(s -> s.replaceAll("\\.", "\\\\."))
                .map(s -> s.replaceAll("([\\(\\)])", "\\\\$1"))
                .collect(Collectors.toSet());
        String regex = String.join("|", regexSet);
        List<String> result = new ArrayList<>();
        Pattern pattern = Pattern.compile(regex);
        for (String phoneNumber : invalidAndValidPhoneNumbers) {
            Matcher matcher = pattern.matcher(phoneNumber);
            if(matcher.matches()) {
                result.add(matcher.group());
            }
        }
        // Output:
        if(uniqueValidPhoneNumbersFormats.size() == result.size()) {
            System.out.println("All valid numbers was matched!\n");
        }    
        result.forEach(System.out::println); 
    }
}
Output:
All valid numbers was matched!
1-234-567-8901
1-234-567-8901 x1234
1-234-567-8901 ext1234
...
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