...Set the java version to compile to. The default is 6. Only 5, 6 or 7 are accepted. The default version of retrolambda used is 'net.orfjackal.retrolambda:retrolambda:2.5.6'. If you want to use a different one, you can configure it in your dependencies. If you are running with java 6 or 7 you should really consider updating. First try updating to the latest version of the android gradle plugin.