Aljoscha Krettek I guess caused this because of java version mismatch. And J2SE 8 belongs to 52. The error message to
Unsupported major.minor version 52.0
is because during compile time using a higher JDK and a lower JDK during runtime here is jdk7 belongs to 51. I dont know how Travis works, it might be travis compile the source code on a machine which use JDK8 and run .class file on a jdk7 machine.