Hey fellow code-slingers! Ever wondered if you could execute code from inside a comment? Sounds wild, right? But with Java nothing is "impassable", and it's *adorably* dangerous 🥺
The Secret Unicode Escape Hatch
So here's the deal. Java lets you use Unicode escapes literally *anywhere* in your source code. That includes places where you'd never expect them to do anything... like inside a one-line comment!
For example, check this out:
// \u000d System.out.println("Surprise! This runs.");
Yup. That \u000d is the Unicode escape for a carriage return (same effect as a new line). So what
happens?
Well, the Java compiler sees that line and, thanks to Unicode processing that happens *before* parsing, it becomes:
//
System.out.println("Surprise! This runs.");
So the comment ends early, and your sneaky little code line executes. Nifty? Terrifying? Maybe a bit of both.
"It's not a bug, it's a feature (with side effects)." - Senior Java Developer
This works because Java compilers treat Unicode escapes as literal characters *before* any actual parsing or comment stripping happens. That's why you can even name your variables in Japanese, Arabic, or Klingon if you're feeling bold.â–ˆ