No more openjdk in Travis.
No more openjdk in Travis.

wselwood/jgrapht,wselwood/jgrapht,WorstCase00/jgrapht,WorstCase00/jgrapht,arcanefoam/jgrapht,WorstCase00/jgrapht,WorstCase00/jgrapht,arcanefoam/jgrapht