Recently I have worked on a 'boring' Java project which uses OpenJDK 7. I want to continuous integrate that project using CircleCI and I had tried to build it on a Linux Ubuntu 14.04 (Trusty), which is the newest version that CircleCI offers. While doing so, I encountered a problem, which, after narrowed down the scope, I found that not occur when I used OracleJDK or build on Linux Ubuntu 12.04 (Precise).
I don't want to downgrade the OS version and I still have not figured out what goes wrong with OpenJDK, so I have temporarily chosen OracleJDK on Ubuntu 14.04. I also stay with version 7 because I don't want to upgrade the JDK version to version 8.
CircleCI Ubuntu 14.04 does not have OracleJDK 7 pre-installed
As mentioned in CircleCI build images page, CircleCI's Ubuntu 14.04 machines has JDK 6, 7, 8 pre-installed, both OracleJDK and OpenJDK; and oraclejdk7 is the default version unless you describe a version you want in the machine section, like: