If you are using Maven or Gradle, add the following dependency to the dependencies section of your project descriptor to access the Vert.x Core API:

- Maven (in your `pom.xml`):

    <dependency>
     <groupId>io.vertx</groupId>
     <artifactId>vertx-core</artifactId>
     <version>3.9.4</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    dependencies {
     compile 'io.vertx:vertx-core:3.9.4'
    }