1. Add cobertura-maven-plugin plugin to your pom.xml files, see here
2. Call mvn cobertura:cobertura during your CI tests, see here
3. Call bash <(curl -s https://codecov.io/bash) at the end of your CI build, see here

• Using Travis CI, CircleCI or AppVeyor AND the repository is public? You're done! No token needed.
• Otherwise, please add this your repository token token.

Other Examples1

• Java JaCoCo Example
• Android Example
• Gradle Example