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.
Yes. They are doing different things and just happen to live on the same page. For example, suppose I have buttons for "add" and "delete." These do different things and are going to have different sequence diagrams.