how bad are exceptions vs performance in a tight loop, really? especially with modern JVMs...

result.md

Turns out the results are quite bad:

$ time java ThrowCounter ex
throw test
count is 5000000

real	0m3.243s
user	0m3.197s
sys	0m0.081s

$ time java ThrowCounter
boolean test
count is 5000000

real	0m0.136s
user	0m0.101s
sys	0m0.035s

ThrowCounter.java

public class ThrowCounter {

    public static void main(String[] args) {
        if (args.length == 0 || args[0].equalsIgnoreCase("bool")) {
            runBooleanTest();
        } else {
            runThrowTest();
        }
    }

    private static void runBooleanTest() {
        System.out.println("boolean test");
        int counter = 0;
        for (int i=0; i < 10_000_000; i++) {
            if (checkEven(i)) {
                counter++;
            }
        }
        System.out.println("count is " + counter);
    }

    private static boolean checkEven(int i) {
        return i % 2 == 0;
    }


    private static void runThrowTest() {
        System.out.println("throw test");
        int counter = 0;
        for(int i=0; i < 10_000_000; i++) {
            try {
                checkEvenException(i);
            } catch (Exception e) {
                counter++;
            }
        }
        System.out.println("count is " + counter);
    }

    private static void checkEvenException(int i) throws Exception {
        if (i % 2 == 0) {
            throw new Exception("even!");
        }
    }
}