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>3.5.3.CR1</version>
    </dependency>

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

    dependencies {
      compile 'io.vertx:vertx-core:3.5.3.CR1'
    }