Get domain name from given URL

core-java-modules/core-java-networking/src/main/java/com/baeldung/networking/domain_name/DomainNameClient.java

@@ -0,0 +1,34 @@
+package com.baeldung.networking.domain_name;
+
+import com.google.common.net.InternetDomainName;
+
+import java.net.URI;
+import java.net.URISyntaxException;
+
+public class DomainNameClient {
+
+    public String getHost(String url) throws URISyntaxException {
+        URI uri = new URI(url);
+        return uri.getHost();
+    }
+
+    public String getTopPrivateDomain(String url) {
+        InternetDomainName internetDomainName = InternetDomainName.from(url)
+            .topPrivateDomain();
+        return internetDomainName.toString();
+    }
+
+    public String getName(String url) {
+        InternetDomainName internetDomainName = InternetDomainName.from(url)
+            .topPrivateDomain();
+        String publicSuffix = internetDomainName.publicSuffix()
+            .toString();
+        String domainName = internetDomainName.toString();
+        return domainName.substring(0, domainName.lastIndexOf("." + publicSuffix));
+    }
+
+    public String getDomainName(String url) {
+        String regex = "http(s)?://|www\\.|/.*";
+        return url.replaceAll(regex, "");
+    }
+}

core-java-modules/core-java-networking/src/test/java/com/baeldung/networking/domain_name/DomainNameClientUnitTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.networking.domain_name;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class DomainNameClientUnitTest {
+
+    DomainNameClient domainNameClient = new DomainNameClient();
+
+    @Test
+    void givenUrl_whenGetHost_thenReturnSubdomainAndDomainName() {
+        Assertions.assertAll(() -> {
+            assertEquals("www.baeldung.com", domainNameClient.getHost("https://www.baeldung.com/domain"));
+            assertEquals("www.google.co.uk", domainNameClient.getHost("https://www.google.co.uk/domain"));
+            assertEquals("jira.baeldung.com", domainNameClient.getHost("https://jira.baeldung.com/secure"));
+        });
+    }
+
+    @Test
+    void givenUrl_whenGetTopPrivateDomain_thenReturnDomainName() {
+        assertEquals("baeldung.com", domainNameClient.getTopPrivateDomain("www.baeldung.com"));
+    }
+
+    @Test
+    void givenUrlWithPublicSuffix_whenGetTopPrivateDomain_thenReturnDomainName() {
+        assertEquals("google.co.uk", domainNameClient.getTopPrivateDomain("www.google.co.uk"));
+        assertEquals("baeldung.blogspot.com", domainNameClient.getTopPrivateDomain("www.baeldung.blogspot.com"));
+    }
+
+    @Test
+    void givenUrlWithPublicSuffix_whenGetName_thenReturnSecondLevelDomain() {
+        assertEquals("baeldung", domainNameClient.getName("jira.baeldung.com"));
+    }
+
+    @Test
+    void givenUrlWithPublicSuffix_whenGetName_thenReturnThirdLevelDomain() {
+        assertEquals("baeldung", domainNameClient.getName("www.baeldung.co.uk"));
+        assertEquals("google", domainNameClient.getName("www.google.co.uk"));
+    }
+
+    @Test
+    void givenUrl_whenGetDomainNameRegex_thenReturnDomainName() {
+        assertEquals("google.com", domainNameClient.getDomainName("www.google.com"));
+        assertEquals("google.co.uk", domainNameClient.getDomainName("www.google.co.uk"));
+        assertEquals("jira.baeldung.com", domainNameClient.getDomainName("jira.baeldung.com"));
+        assertEquals("baeldung.com", domainNameClient.getDomainName("www.baeldung.com/test"));
+    }
+
+}