public boolean yankPop() throws IOException {
        if (!killRing.lastYank()) {
            return false;
        }
        String current = killRing.yank();
        if (current == null) {
            // This shouldn't happen.
            return false;
        }
        backspace(current.length());
        String yanked = killRing.yankPop();
        if (yanked == null) {
            // This shouldn't happen.
            return false;
        }

        putString(yanked);
        return true;
    }