public class App {

    public static void main(String[] args) throws Exception {

        System.out.println("Java Version: " + System.getProperty("java.vm.version"));

        for (int i = 0; true; i++) {
            for (int j = 0; j < 100; j++) {
                // short delay (required)
            }

            String s = "hello";
            s = new StringBuilder(String.valueOf(s)).append(s).toString();
            s = new StringBuilder(String.valueOf(s)).append(s).toString();

            if (s.length() != 20) {
                System.out.println("Failed at iteration: " + i);
                System.out.println("Length mismatch: " + s.length() + " <> " + 16);
                System.out.println("Expected:   \"hellohellohellohello\"");
                System.out.println("Actual:   \"" + s + "\"");
                System.exit(0);
            }
        }
    }
}