Since String.length() method returns an int we could guess that the maximum length would be Integer.MAX_VALUE characters. That’s not correct. Let’s forget about Unicode for now, and try to create the longest possible string by repeating a lowercase letter a.

In one of my favourite presentations Why you should avoid Linked Lists we see a comparison of C++ vector and list performance in the following problem:

When optimizing an algorithm it’s often good to pause, take a step back, and think about the problem domain before jumping straight to coding. Today I have seen following question asked on Stack Overflow:

java.util.WeakHashMap can be used as in-memory cache, allowing keys to expire when they are weakly reachable. Unfortunately this class is not thread-safe. It’s entirely possible that un-synchronized invocation of the WeakHashMap.get(Object) method will result in infinite busy waiting loop starving all other threads.

One of my highest voted posts on Stack Overflow is an answer to Deserialize enum ignoring case in Spring Boot controller question. Frankly, the answer is incorrect. The whole situation is puzzling since I don’t get why it was upvoted.

Stack Overflow was launched over 11 years ago. Since then more than 19 million questions were asked and only Jon Skeet read them all. Below you can find a handful of my favourite questions. Each of them is answered in depth, providing a chance to learn something interesting.