- Spring Boot – Configuring the Security Filter Chain
The modern lambda DSL — WebSecurityCustomizer is gone and so is WebSecurityConfigurerAdapter. Ordering rules so a permitAll does not accidentally open an admin endpoint, disabling CSRF only where it is genuinely safe to, and making CORS and security agree instead of fighting.
- Python – Decorators
Decorators, built up from the one fact that makes them possible: functions are objects. Writing one, passing arguments through it, why `functools.wraps` is not optional, and the built-in decorators you already use.
- Java 17 Pattern Matching for instanceof
Every instanceof check used to be followed by a cast to the type you had just checked for. Pattern matching folds the two into one, and the compiler tracks where the result is valid. It is a small change that removes a line from a very common shape. The old shape s is a pattern variable . It exists…
- Java 17 Text Blocks
A text block is a string literal delimited by three quotes that can span lines without escaping. It exists because embedded JSON, SQL and HTML were genuinely painful to read in Java, and the workarounds — concatenation, \n everywhere, external files — were all worse than the problem. The problem…
- Divide and Conquer
Split the problem into independent subproblems, solve each, combine. The word doing the work is independent — that is exactly what separates this from dynamic programming. Fast exponentiation, and counting inversions for free inside a merge.