A search comparing the StringCollection to the ArrayList may give you articles that say "the ArrayList works better than the StringCollection" but what you need to know is that a StringCollection is simply extra methods over an ArrayList - there is an actual ArrayList included as a private member within the StringCollection class and it caters to storage needs of StringCollection. In other words, the StringCollection is just a disguised ArrayList!
You don't really have to decide between using an ArrayList or the StringCollection wrapper - both are essentially the same! You use a StringCollection wrapper when you are dealing with strings... the cast to a string is performed by a method in the wrapper so you don't have to do it each time you access it. If you aren't dealing with strings, the StringCollection isn't an option anyway.
If you count the number of pages linking to a Wikipedia page, there may be none but it still appears on the first page of the search results.
Google seems to rank pages from Wikipedia higher up in the results. One possibility is that it doesn't seem to be using the regular PageRank algorithm for some websites. Either that or the PageRank algorithm uses a list of 'favorite domains' when ranking pages. I considered the possibility of 'favorite domains' a little more and Googled it a bit when I came across an article that mentions about Google having access to the domain registration information so I'm guessing that there is a possibility Google checks the age of the wikipedia.org domain registration and factors that in too.