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.
You've got your ArrayList set up correctly. The problem with your code is that floating point numbers default to doubles unless you mark them as floats. So, if you want Java to know you mean floats rather than doubles, you'll need to add an 'f' to the number, like this: 23.05f.