private void setUpMasses() {
        shoulder = new Mass(0, 0);
        inputShoulder = new Mass(1, 0);
        inputElbow1 = new Mass(4, 0);
        elbow = new Mass(5, 0);
        inputElbow2 = new Mass(6, 0);
        inputHand = new Mass(9, 0);
        hand = new Mass(10, 0);

        shoulder.setType(SHOULDER);
        inputShoulder.setType(INPUT);
        inputElbow1.setType(INPUT);
        elbow.setType(ELBOW);
        inputElbow2.setType(INPUT);
        inputHand.setType(INPUT);
        hand.setType(HAND);

        graph.addMasses(shoulder);
        graph.addMasses(inputShoulder);
        graph.addMasses(inputElbow1);
        graph.addMasses(elbow);
        graph.addMasses(inputElbow2);
        graph.addMasses(inputHand);
        graph.addMasses(hand);
    }