How to validate MAC address using Regular Expression

Given a string str, the task is to check whether the given string is valid MAC address or not by using Regular Expression.

A valid MAC address must satisfy the following conditions:

  1. It must contain 12 hexadecimal digits.
  2. One way to represent them is to form six pairs of the characters separated with a hyphen (-) or colon(:). For example, 01-23-45-67-89-AB is a valid MAC address.
  3. Another way to represent them is to form three groups of four hexadecimal digits separated by dots(.). For example, 0123.4567.89AB is a valid MAC address.

Examples:

Input: str = “01-23-45-67-89-AB”;
Output: true
Explanation:
The given string satisfies all the above mentioned conditions. Therefore it is a valid MAC address.

Input: str = “01-23-45-67-89-AH”;
Output: false
Explanation:
The given string contains ‘H’, the valid hexadecimal digits should be followed by letter from a-f, A-F, and 0-9. Therefore it is not a valid MAC address.



Input: str = “01-23-45-67-AH”;
Output: false
Explanation:
The given string has five groups of two hexadecimal digits. Therefore it is not a valid MAC address.

Approach: The idea is to use Regular Expression to solve this problem. The following steps can be followed to compute the answer.

  1. Get the String.
  2. Create a regular expression to check valid MAC address as mentioned below:

    regex = “^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})|([0-9a-fA-F]{4}\\.[0-9a-fA-F]{4}\\.[0-9a-fA-F]{4})$”;

    Where:

    • ^ represents the starting of the string.
    • ([0-9A-Fa-f]{2}[:-]){5} represents the five groups of two hexadecimal digits separated by hyphens (-) or colons (:)
    • ([0-9A-Fa-f]{2}) represents the one groups of two hexadecimal digits.
    • | represents the or.
    • ( represents the starting of the group.
    • [0-9a-fA-F]{4}\\. represents the first part of four hexadecimal digits separated by dots (.).
    • [0-9a-fA-F]{4}\\. represents the second part of four hexadecimal digits separated by dots (.).
    • [0-9a-fA-F]{4} represents the third part of four hexadecimal digits.
    • ) represents the ending of the group.
    • $ represents the ending of the string.
  3. Match the given string with the Regular Expression. In Java, this can be done by using Pattern.matcher().
  4. Return true if the string matches with the given regular expression, else return false.

Below is the implementation of the above approach:

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// Java program to validate
// MAC address using
// regular expression
  
import java.util.regex.*;
class GFG {
  
    // Function to validate
    // MAC address
    // using regular expression
    public static boolean
    isValidMACAddress(String str)
    {
        // Regex to check valid
        // MAC address
        String regex
            = "^([0-9A-Fa-f]{2}[:-])"
              + "{5}([0-9A-Fa-f]{2})|"
              + "([0-9a-fA-F]{4}\\."
              + "[0-9a-fA-F]{4}\\."
              + "[0-9a-fA-F]{4})$";
  
        // Compile the ReGex
        Pattern p = Pattern.compile(regex);
  
        // If the string is empty
        // return false
        if (str == null) {
            return false;
        }
  
        // Find match between given string
        // and regular expression
        // uSing Pattern.matcher()
  
        Matcher m = p.matcher(str);
  
        // Return if the string
        // matched the ReGex
        return m.matches();
    }
  
    // Driver code
    public static void main(String args[])
    {
  
        // Test Case 1:
        String str2 = "01-23-45-67-89-AB";
        System.out.println(
            isValidMACAddress(str2));
  
        // Test Case 2:
        String str3 = "01:23:45:67:89:AB";
        System.out.println(
            isValidMACAddress(str3));
  
        // Test Case 3:
        String str1 = "0123.4567.89AB";
        System.out.println(
            isValidMACAddress(str1));
  
        // Test Case 4:
        String str4 = "01-23-45-67-89-AH";
        System.out.println(
            isValidMACAddress(str4));
  
        // Test Case 5:
        String str5 = "01-23-45-67-AH";
        System.out.println(
            isValidMACAddress(str5));
    }
}

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Output:

true
true
true
false
false

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