Design

• We do not know how many URLs there will be when we start parsing so let's use a Vector

• Single threaded for simplicity but a real program would use multiple threads

• The character data of each URL element needs to be stored. Everything else can be ignored.

• A startElement() with the name url indicates that we need to start storing this data.

• A stopElement() with the name url indicates that we need to stop storing this data, convert it to a URL and put it in the Vector

• Hide the XML parsing inside a non-public class to avoid accidentally calling the methods from unexpected places or threads?