String userName = "<user-name>";
String password = "<password>";
String resourceGroupName = "<resource-group-name>";
String name = "<webapp-name>";

ServiceClientCredentials credentials = new BasicAuthenticationCredentials(userName, password);
WebSiteManagementClient webSiteManagementClient = new WebSiteManagementClientImpl(credentials);
HostingEnvironmentsOperations hostingEnvironmentsOperations = webSiteManagementClient.getHostingEnvironmentsOperations();
ServiceResponse<AddressResponse> serviceResponse = hostingEnvironmentsOperations.getHostingEnvironmentVips(resourceGroupName, name);

AddressResponse addressResponse = (AddressResponse) serviceResponse.getBody();
String internalIp = addressResponse.getInternalIpAddress();

<dependency>
    <groupId>com.microsoft.azure</groupId>
    <artifactId>azure-svc-mgmt-websites</artifactId>
    <version>0.9.2</version>
</dependency>