Exceptions: a stackless exception skips capturing a stack trace for speed

The protected Throwable(String, Throwable, boolean, boolean) constructor can disable stack trace capture, which is much cheaper for exceptions thrown very frequently for control flow rather than for diagnosing bugs.

Code

class FastSignal extends RuntimeException {
    FastSignal(String message) {
        super(message, null, false, false);
    }
}
try {
    throw new FastSignal("stackless");
} catch (FastSignal e) {
    System.out.println(e.getClass().getSimpleName() + ": " + e.getMessage());
    System.out.println("Stack trace length: " + e.getStackTrace().length);
}

Output

FastSignal: stackless
Stack trace length: 0