java check ipv6 with regex

To check if a string represents a valid IPv6 address using regular expressions in Java, you can use the matches method of the String class and a regular expression that defines the pattern of a valid IPv6 address.

Here's an example of how to use the matches method and a regular expression to check if a string represents a valid IPv6 address:

public class Main {
  public static void main(String[] args) {
    String ipv6 = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";

    if (ipv6.matches("^([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}$")) {
      // string is a valid IPv6 address
    } else {
      // string is not a valid IPv6 address
    }
  }
}

In this example, the regular expression "^([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}$" defines the pattern of a valid IPv6 address. The matches method is used to check if the string ipv6 matches this pattern.

The regular expression consists of 8 groups of 1 to 4 hexadecimal digits separated by colons, and anchored to the beginning and end of the string with the ^ and $ characters.