I've attached a zipped NetBeans project that contains all the worked exercises combined into a single project.
I encourage you to attempt the problems yourself before "peeking" at the solutions.
The solutions I've provided are just one of many possible ways to achieve the same effect. If your code is different, but still works, it doesn't necessarily mean that you are "wrong". In fact, your solution may be better than the ones that I have provided. I suggest looking at the differences and understanding why you and I have made different design choices.
I've added an index.html page that will take you to each of the solutions (you can see it by just clicking the run button [green triangle] in NetBeans).
Note that I've also added a "BetterSessionCounter" which is the same as the session counter but has a (possibly) better design.