Use regular expressions to determine if a string is a MAC address

Today boss gives a small task, asking for a string to determine whether the string is a MAC address and implemented with Java and regular expressions. So I by the way Baidu the next MAC address, and CMD under the use of Getmac to get the MAC address of the machine, understand a bit, it is implemented with Java. To facilitate testing and input and output, select Use Android as UI interaction. Anyway, with Java, for this problem, a Java project and Android are not very different.

First look at a MAC address: 48-5d-60-61-3d-c5. It consists of 6 bytes (hexadecimal), simple to understand the number of characters, uppercase and lowercase letters (a-fa-f), dashes-composition. Nonsense not to say, first write a regular expression of the Mac, I wrote a total of 3 regular expressions, is the result of continuous optimization.

Regular Expressions:

(1) "[a-fa-f0-9][a-fa-f0-9]-[a-fa-f0-9][a-fa-f0-9]-[a-fa-f0-9][a-fa-f0-9]-[a-fa-f0-9][a-fa-f0-9]-[a-fa-f0-9][ A-FA-F0-9]-[A-FA-F0-9][A-FA-F0-9] "

Although this expression looks long, it is the simplest of logic, the easiest to understand, and exactly right. A-f a-f 0-9 means one of them, the middle is a "or" relationship. Dash-can be matched directly.

(2) "[A-fa-f0-9]{2}-[a-fa-f0-9]{2}-[a-fa-f0-9]{2}-[a-fa-f0-9]{2}-[a-fa-f0-9]{2}-[a-fa-f0-9]{2}"

After optimization, the length is cut half short. {2} is to loop the previous part 2 times. On the basis of the first method, this is also easy to understand.

(3) "([a-fa-f0-9]{2}-) {5}[a-fa-f0-9]{2}"

Continue optimization on the basis of (2). The "[a-fa-f0-9]{2}-" is extracted as a unit. {5} and loop 5 times, because the polygon and the front 5 are duplicates, there is a lot of compressed space.

Code writing is simple and visually programmed on Android:

public class Mainactivity extends Activity {private EditText ismac;private Button startmac;private TextView Result;privat e static String judgemacaddress; @Overrideprotected void OnCreate (Bundle savedinstancestate) {super.oncreate ( Savedinstancestate); Setcontentview (r.layout.activity_main); Ismac = (EditText) Findviewbyid (r.id.id_edit); StartMAC = (Button) Findviewbyid (r.id.id_btn); result = (TextView) Findviewbyid (R.id.id_text); Startmac.setonclicklistener (new Onclicklistener () {@Overridepublic void OnClick (View v) {judgemacaddress = Ismac.gettext (). ToString (); Boolean ismac = Stringismac (judgemacaddress); if (Ismac) {Result.settext ("This is MAC Address");} else {Result.settext ("This is not a MAC address");}});} Private Boolean Stringismac (String val) {String truemacaddress = "([a-fa-f0-9]{2}-) {5}[a-fa-f0-9]{2}";//This is the real MAV address , regular expression, if (Val.matches (truemacaddress)) {return true;} else {return false;}}}

(1) (2) (3) The result of the final implementation is as follows:

.

At this point, the MAC address has been judged. Perhaps the final type of regular expression and the method of optimization, please give criticism and suggestions.

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Use regular expressions to determine if a string is a MAC address