Since Java is a network-centric multi-threaded language that is heavily used for creating servers that communicate with databases, an app in that direction would probably quite company oriented. The problem here is that almost all books have exhausted examples for exactly that -- in Head First Java they actually describe how to write a Chat client & server, and there won't be a book without a chapter about databases and JDBC.
So in this regard, a card game playable over the Internet would stand out as something different and more interesting, I'd say. Besides the networking part, it would also contain a not so trivial GUI part, so you could show off more of your skills. ;-)
By the way, if you want to read a quite good book about networking in Java, I can recommend "Fundamental Networking in Java" by Esmond Pitt, published by Springer, ISBN 1-84628-030-3. The guy knows very well what he is talking about, but I'm afraid that the code samples in the book at the same time show what a horrible language Java can be even for its "core business" - especially when you compare it to a clean and efficient language like Python. But I don't wanna go into language bashing here, you have some good business reasons to learn Java and those cannot be talked away. ;-)
Coming back to your ideas, I think the card game is cool, and it could store some data about the players and their matches in a database. The chat applet should NOT rely on PHP scripts to communicate with the database, but rather take advantage of MySQL AB's JDBC driver. Unless, of course, you also want to demonstrate your mastering of that scripting language or cannot access the MySQL db directly over the net. Would it be possible for you to have an own Java app running directly on the server? If so, you could write an own server.
So in this regard, a card game playable over the Internet would stand out as something different and more interesting, I'd say. Besides the networking part, it would also contain a not so trivial GUI part, so you could show off more of your skills. ;-)
By the way, if you want to read a quite good book about networking in Java, I can recommend "Fundamental Networking in Java" by Esmond Pitt, published by Springer, ISBN 1-84628-030-3. The guy knows very well what he is talking about, but I'm afraid that the code samples in the book at the same time show what a horrible language Java can be even for its "core business" - especially when you compare it to a clean and efficient language like Python. But I don't wanna go into language bashing here, you have some good business reasons to learn Java and those cannot be talked away. ;-)
Coming back to your ideas, I think the card game is cool, and it could store some data about the players and their matches in a database. The chat applet should NOT rely on PHP scripts to communicate with the database, but rather take advantage of MySQL AB's JDBC driver. Unless, of course, you also want to demonstrate your mastering of that scripting language or cannot access the MySQL db directly over the net. Would it be possible for you to have an own Java app running directly on the server? If so, you could write an own server.