Codename One - RegexConstraint to check a valid phone number - codenameone

Question

In the following code, the RegexConstraint doesn't work, because the phone number results always incorrect. What's wrong? I need to check a mobile phone number (without the country code). For example, the input 3652312453 should be correct, but in the following code it's evaluated as incorrect.
I copied the regex from the discussion linked in the comment: my only requirement is a valid phone number.
(Note: this question is not for generic Java, but only for Codename One. The class "CountryCodePicker" extends the class "Button": I reported it to make it clear that the phone number and the country code are separated)
TextModeLayout tl = new TextModeLayout(1, 1);
Container loginContainer = new Container(tl);
TextComponent phone = new TextComponent().label("PHONE").errorMessage("INVALID-PHONE");
CountryCodePicker countryCode = new CountryCodePicker();
phone.getField().setConstraint(TextArea.PHONENUMBER);
loginContainer.add(phone);
Container loginContainerWithCodePicker = new Container(new BoxLayout(BoxLayout.X_AXIS_NO_GROW));
loginContainerWithCodePicker.add(countryCode).add(loginContainer);
// https://stackoverflow.com/questions/8634139/phone-validation-regex
String phoneRegEx = "/\\(?([0-9]{3})\\)?([ .-]?)([0-9]{3})\\2([0-9]{4})/";
val.addConstraint(phone, new RegexConstraint(phoneRegEx, "NOT-VALID-NUMBER"));
Button loginButton = new Button("LOG-IN");
val.addSubmitButtons(loginButton);

Answer 1

[rant]
Personally I really hate regex as I find it damn unreadable for anything other than trivial validation.
[/rant]
So I would prefer this:
val.addConstraint(phone, new Constraint() {
public boolean isValid(Object value) {
String v = (String)value;
for(int i = 0 ; i < v.length() ; i++) {
char c = v.charAt(i);
if(c >= '0' && c <= '9' || c == '+' || c == '-') {
continue;
}
return false;
}
return true;
}
public String getDefaultFailMessage() {
return "Must be valid phone number";
}
});
However, I'm guessing the reason the regex failed for you is related to the syntax with the slashes:
String phoneRegEx = "^\\(?([0-9]{3})\\)?([ .-]?)([0-9]{3})\\2([0-9]{4})";

Answer 2

The following resource on Oracle's Java 8 Lessons helps me always define the RegEx I need. Take the time to study it and you will be successful, especially since the problem seems to be in the initialization of the Constraint object. I had an issue the day before my post here, and managed to solve it elegantly which is the goal, always.
Use this link
https://docs.oracle.com/javase/tutorial/essential/regex/
Oracle Tutorials: "Lesson: Regular Expressions".