[guelo]

@Nullable/@NotNull is great when the IDE shows the warnings, basically dev time checking. There are also tools to integrate it into your builds for compile time checking.

[mrkeen]

I get a little green tick in the top right of my IDE window with the following:

    @Test
    public void foo() {
        final Map<String, Integer> map = new HashMap<>();
        map.put("present", 1);
        bar(map.get("missing"));
    }

    void bar(@NotNull Integer param) {
        System.out.println(param);
    }

"No problems found"

[guelo]

Right, that's because the system libraries don't have the annotations. That's the biggest issue with it. But it still helps a lot if you're religious about it in your own code.