Added README.md file.

src/main/java/com/example/JavaAzureAppConfigApplication.java

@@ -7,9 +7,10 @@ import com.example.service.AzureAppConfigService;
 
 public class JavaAzureAppConfigApplication {
 
+    private static final String APP_CONNECTION_STRING = System.getenv("APP_CONFIGURATION_CONNECTION_STRING");
+
     public static void main(String[] args) {
-        String app_configuration_connection_string = System.getenv("APP_CONFIGURATION_CONNECTION_STRING");
-        ConfigurationClient configurationClient = new ConfigurationClientBuilder().connectionString(app_configuration_connection_string).buildClient();
+        ConfigurationClient configurationClient = new ConfigurationClientBuilder().connectionString(APP_CONNECTION_STRING).buildClient();
         new AzureAppConfigService(configurationClient, new SettingSelector()).azureAppConfiguration();
     }
 }