Style: Add checkstyle rule to prevent using Objects.requireNonNull

[tal66]

Hi, this closes #4613.

running the checks on this simple example, :

    public static void main(String[] args)  {
        String str = null;

        // not allowed
        Objects.nonNull(str);
        Objects.nonNull(Integer.valueOf(123));
        Objects.requireNonNull(str);
        Objects.requireNonNullElse(str, "123");
        Objects.requireNonNullElseGet(str, () -> "1");

        // allowed
        Objects.isNull(str);
    }

generates: <error line="..." severity="error" message="Prefer using Preconditions.checkNotNull(Object, String)." source=... for the 'not allowed' lines above.

[kbendick]

I tried this locally with Objects.requireNonNull(obj) and Objects.requireNonNull(obj, "error message) and both of them failed checkstyle.

LGTM provided tests are passing. Thanks @tal66!

[singhpk234]

LGTM as well, Thanks @tal66

[rdblue]

Thanks, @tal66!

[nastra]

just curious, why wouldn't we want to allow something like if (Objects.nonNull(x))? The checkstyle message suggests to use Preconditions.checkNotNull instead, but that's not really the same. I can see why we'd want to use Preconditions.checkNotNull rather than Objects.requireNonNull but not why we'd prevent usage of Objects.nonNull, since it's just returning a boolean