This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
In changeIt, myBar = new Bar(); is assigning a new instance to the method parameter myBar, not to the instance variable. myBar.barNum = 99 sets the instance variable to 99, because the instance variable was passed to the method (i.e. method parameter = instance variable).