public void setMass(PhysicsLink link, float mass) {
        if (link instanceof BoneLink) {
            String boneName = link.boneName();
            setMass(boneName, mass);
        } else {
            assert link instanceof TorsoLink;
            setMass(torsoName, mass);
        }
    }
Alter the mass of the specified link.

@param link the link to modify (not null)
@param mass the desired mass (&gt;0)
jme3-jbullet/src/main/java/com/jme3/bullet/animation/DacLinks.java