Kara walks around the trees in an endless loop. In each step, he considers the sensors "tree front?" and "tree right?" to determine the appropriate action.
while (true) { if (kara.treeFront() && kara.treeRight()) { kara.turnLeft(); } else if (!kara.treeFront()) if (kara.treeRight()) { kara.move(); } else { kara.turnRight(); kara.move(); } }