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.
If the question was something like "Explain how you would build a dictionary using only the core java libraries", that is a likely question (got one similar in an exam).
To start you may want to see what exactly a dictionary is. It seems to me it is a word with the meaning in front of it. So, you have a word, that does not repeat, and a series of words that relates to it. Doesn't that sound like something?