Extract domain name using Java regular expression

Friday, 17 June 2011 10:10

Extract domain name using Java regular expressions

In this sample we are using Java regular expressions to extract domain names.

Java method to extract domains

Let's define the regular expression pattern :

private List<String> extractDomains(String value){
    if (value == null) throw new NullArgumentException("domains to extract");
    List<String> result = new ArrayList<String>();
    String domainPattern = "[a-z0-9\\-\\.]+\\.(com|org|net|mil|edu|(co\\.[a-z].))";
    Pattern p = Pattern.compile(domainPattern,Pattern.CASE_INSENSITIVE);
    Matcher m = p.matcher(value);
    while (m.find()) {
        result.add(value.substring(m.start(0),m.end(0)));
    }
    return result;
}

Extracting the domain using our Pattern

If you execute our method using the following content :

www.subdomain.domain.com www.google.co www.google.co.in www.google.com www.facebook.com  www.google.co.tw

Using the following sample code to execute our method :

String content = " www.subdomain.domain.com www.google.co www.google.co.in www.google.com www.facebook.com www.google.co.tw "; 
List<string> domains = extractDomains(content); 
for (String domain : domains) 
{
    System.out.println("domain :" + domain); 
} 

domain :www.subdomain.domain.com
domain :www.google.co.in
domain :www.google.com
domain :www.facebook.com
domain :www.google.co.tw

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• Extacting Url using regular expressions