正則表達式不正確匹配限制值

Question

我創建了一個正則表達式來檢查電子郵件地址是否有管理員，固件，服務&修復。如果我在電子郵件地址中輸入'ad'而不是'admin'，那麼它也會根據要求返回true，這是不正確的。

private static final String EMAIL_PATTERN_New = 
      "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@" 
      + "[admin|firmware|repair|service]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$"; 

static String email = "xxxx@admin.com"; 
static String email1 = "xxxx@ad.com"; 
static String email2 = "test@irm.jdsu.com"; 
public static boolean validate(final String hex) { 
     pattern = Pattern.compile(EMAIL_PATTERN_New); 
     matcher = pattern.matcher(hex); 
     return matcher.matches(); 
    } 
System.out.println(validate(email));  //true 
System.out.println(validate(email1));  //true but it should be false 
System.out.println(validate(email2)); //true but it should be false 

與其他電子郵件地址相同的固件，服務，修理。

Answer 1

您需要用(admin|firmware|repair|service)替換[admin|firmware|repair|service]+。

參見this regex demo

[admin|firmware|repair|service]+的是一個字符類匹配單獨的字符，a，d等一次或多次（由於+）。因此，它將匹配ad，add，fir等

的(admin|firmware|repair|service)是序列分組結構，只要符合admin，或firmware等

注意，您可以通過縮短Java中的正則表達式與\w更換[_a-zA-Z0-9]：

private static final String EMAIL_PATTERN_New = "^[\\w+-]+(?:\\.[\\w-]+)*@(?:admin|firmware|repair|service)(?:\\.[A-Za-z0-9]+)*\\.[A-Za-z]{2,}$"; 

你甚至可以刪除^和$因爲您正在使用matches()方法的正則表達式。

Java demo from IDEONE：

import java.util.*; 
import java.util.regex.*; 
import java.lang.*; 
import java.io.*; 

class Ideone 
{ 
    private static final String EMAIL_PATTERN_New = 
      "^[\\w+-]+(?:\\.[\\w-]+)*@(?:admin|firmware|repair|service)(?:\\.[A-Za-z0-9]+)*\\.[A-Za-z]{2,}$"; 

    public static void main (String[] args) throws java.lang.Exception 
    { 
     String email = "xxxx@admin.com"; 
     String email1 = "xxxx@ad.com"; 
     String email2 = "test@irm.jdsu.com"; 

     System.out.println(email.matches(EMAIL_PATTERN_New));  // true 
     System.out.println(email1.matches(EMAIL_PATTERN_New)); // false 
     System.out.println(email2.matches(EMAIL_PATTERN_New)); // false 
    } 
}