A couple of years ago Google launched an interesting website: Google Foobar. If you try to log in, you'll get an error saying:
To login, you have to have logged in before. Confused? Search on...
Pretty mysterious, right? Well, from what I read on Hacker News at the time, this is some kind of a puzzle set up by Google to recruit Python and Java developers. To get in, you'd simply have to search for the correct phrase. Someone reported that searching for "arraylist java" got him inside, but that didn't work for me.
However, I recently found that searching for this actually gets you inside, but you have to be a little bit patient. Here's what you can do:
Open a browser of your choice (it has to be a sufficiently new version so you get the newest version of Google). I've only tested this successfully with Chrome and Firefox.
Go to https://google.com/ncr. (The /ncr at the end is to make sure you go to the main version of Google. Don't know if that's necessary, but doesn't hurt)
Search for "arraylist java" or "python list comprehension". Other programming-related search terms may also work, but these should definitely work.
Here comes the "be a little bit patient" part. Copy the URL for the search results page that you just got (Ctrl+L, Ctrl+C). Now open a lot of tabs with the same URL (repeat Ctrl+T, Ctrl+V, Enter). I'm not sure how many tabs you need to open, but from my experience 10 tabs should be sufficient.
Wait for each of the tabs to load. Then go through them, one by one, and look for a tab that contains a black banner saying "You're speaking our language. Up for a challenge?" at the top of the search results. (If you don't get any tab with this banner, try going back to step 1, possibly using a different browser.)
Click "I want to play". You're in!
Now you will be presented with a terminal that you can use to solve some competitive programming-style problems using Java or Python. They start easy and become progressively harder, and each problem has a certain time frame you have to solve it within.
When you've progressed to the third or fourth level (don't remember which one), you get the opportunity to send your code to Google recruiters. From what I've read online, this has lead to some people getting an interview at Google. So if you're interested in that, this might be your chance! If not, it's still a bunch of fun problems to solve. :)