Is there a reason to display scrollbars only when they are needed, as opposed to displaying them all the time?

Normally, the decision is based on how you want the interface to look. Some interface designers prefer to have the scrollbars visible at all times, while others make them visible only when the component needs them. With early implementations of scroll panes in Java 2, scrollbars would disappear in certain instances and never reappear. Though this appears to have been resolved, making scrollbars visible at all times is a way to work around a problem like this.

How can I find out about the rest of the Swing classes in the Java class library?

On Sun's official Java site, the full documentation for the Java class library is published at http://java.oracle.com/j2se/1.5.0/docs/api. You can see the classes that are included in javax.swing, java.awt, and java.awt.event, the packages that were covered during the preceding four hours. All Swing classes and interfaces are documented, including their constructor methods, class variables, and instance variables. There are also links to some of Sun's official tutorials for Swing programmers.

Did they charge admission or have reserved seating at the Colosseum?

Aside from the killing, the fan experience at the Roman Colosseum was similar to today's sporting events. There were 45,000 seats in the amphitheatre and room for up to 5,000 standing fans. Tickets, which were heavily in demand, were marked with the entrance to use as well as the tier and row number of the seat. The emperor rated a luxury box, and senators and other high officials got the best seats. Admission was free, because aspiring politicians bankrolled the events. The Colosseum, known officially as the Flavian Amphitheatre, opened in 80 A.D. Most of the biggest attractions involved people fighting each other or animals. Up to 5,000 animals were killed on Opening Day of the facility.