public void addBody(Body argBody){
  bodies.add(argBody);
  if (bodies.size() == 1) {
    bodyA=argBody;
  }
  if (bodies.size() == 2) {
    bodyB=argBody;
  }
}

public void addBody ( Body argBody ) { bodies . add ( argBody ) ; if ( bodies . size ( ) == 1 ) { bodyA = argBody ; } if ( bodies . size ( ) == 2 ) { bodyB = argBody ; } }
adds a body to the group
