rfc5322　3.4.1. Addr-Spec Specification

メールアドレスの仕様
https://tools.ietf.org/html/rfc5322#page-17

以下抜粋
—-
An addr-spec is a specific Internet identifier that contains a
locally interpreted string followed by the at-sign character (“@”,
ASCII value 64) followed by an Internet domain. The locally
interpreted string is either a quoted-string or a dot-atom. If the
string can be represented as a dot-atom (that is, it contains no
characters other than atext characters or “.” surrounded by atext
characters), then the dot-atom form SHOULD be used and the quoted-
string form SHOULD NOT be used. Comments and folding white space
SHOULD NOT be used around the “@” in the addr-spec.

addr-spec = local-part “@” domain

local-part = dot-atom / quoted-string / obs-local-part

domain = dot-atom / domain-literal / obs-domain

domain-literal = [CFWS] “[” *([FWS] dtext) [FWS] “]” [CFWS]

dtext = %d33-90 / ; Printable US-ASCII
%d94-126 / ; characters not including
obs-dtext ; “[“, “]”, or “\”
——-
使えるのは、半角英数字か、「!#$%&’*+-/=?^_`{|}~」
で、正規表現で書くと、

^[\w!#%&'/=~`\*\+\?\{\}\^\$\-\|]+(\.[\w!#%&'/=~`\*\+\?\{\}\^\$\-\|]+)*@[\w!#%&'/=~`\*\+\?\{\}\^\$\-\|]+(\.[\w!#%&'/=~`\*\+\?\{\}\^\$\-\|]+)*$

実際に試してみる。

import java.util.regex.Matcher;
import java.util.regex.Pattern;

class Playground {
    public static void main(String[ ] args) {
        
        String str = "hogehogehoge.jp";
        
        Pattern p = Pattern.compile("^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\\.[a-zA-Z0-9-]+)*$");
        Matcher m = p.matcher(str);
        
        if(m.find() == true){
            System.out.println("OK");
        } else{
            System.out.println("NG");
        }
        
    }
}

NGとなる。

メールアドレスの判定をする。

public void getScore(View view){


        // edittextを取得
        EditText fEditText = (EditText) findViewById(R.id.firstnEditText);
        EditText lEditText = (EditText) findViewById(R.id.lastnEditText);
        EditText pEditText = (EditText) findViewById(R.id.phoneEditText);
        EditText mEditText = (EditText) findViewById(R.id.mailEditText);
        // edittextの中身を取得
        String firstName = fEditText.getText().toString().trim();
        String lastName = lEditText.getText().toString().trim();
        String myPhone = pEditText.getText().toString().trim();
        String myMail = mEditText.getText().toString().trim();

        Pattern p = Pattern.compile("^[0-9\\-]+");
        Matcher m = p.matcher(myPhone);

        Pattern mp = Pattern.compile("^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\\\\.[a-zA-Z0-9-]+)*$");
        Matcher mm = mp.matcher(myMail);

        // 中身を観て条件分岐
       if (firstName.equals("")){
             fEditText.setError("Please enter your first name!");
        } else if(lastName.equals("")){
           lEditText.setError("Please enter your last name!");
        } else if(myPhone.equals("") || m.find() == false){
           pEditText.setError("Please enter your phone number!");
        }else if(myMail.equals("") || mm.find() == false){
           mEditText.setError("Please enter your valid email");
        } else {
            Intent intent = new Intent(this, MyResult.class);
            intent.putExtra(EXTRA_MYNAME, firstName);
            startActivity(intent);
        }
    }