How to check multiple objects for nullity?

EDIT 2018: As of Apache Commons lang 3.5, there has been ObjectUtils.allNotNull() and ObjectUtils.anyNotNull().

No.

None of Apache Commons Lang (3.4), Google Guava (18) and Spring (4.1.7) provide such a utility method.

You'll need to write it on your own if you really, really need it. In modern Java code, I'd probably consider need for such a construct a code smell, though.


You could also use something like the following method. It allows you to pass as many parameters as you want:

public static boolean isAnyObjectNull(Object... objects) {
    for (Object o: objects) {
        if (o == null) {
            return true;
        }
    }
    return false;
}

You call it with as many parameters as you like:

isAnyObjectNull(a, b, c, d, e, f);

You could do something similar for areAllNull.

public static boolean areAllObjectsNull(Object... objects) {
    for (Object o: objects) {
        if (o != null) {
            return false;
        }
    }
    return true;
}

Note: you could also use the ternary operator instead of if (o == null). The two methods shown here have no error handling. Adjust it to your needs.


In Java 8, you could use Stream.allMatch to check whether all of the values match a certain condition, such as being null. Not much shorter, but maybe a bit easier to read.

if (Stream.of(a, b, c).allMatch(x -> x == null)) {
    ...
}

And analogeously for anyMatch and noneMatch.

About your "more challenging example": In this case, I think there is no way around writing a lazy-evaluated conjunction of null-checks, like the one you have:

if (a != null && a.getFoo() != null && a.getFoo().getBar() != null) {
    ...
}

Any of the other approaches, using streams, lists, or var-arg methods, would try to evaluate a.getFoo() before a has been tested not to be null. You could use Optional with map and method pointers, that will be lazily evaluated one after the other, but whether this makes it any more readable is debatable and may vary from case to case (particularly for longer class names):

if (Optional.ofNullable(a).map(A::getFoo).map(B::getBar).isPresent()) {
    ...
}

Bar bar = Optional.ofNullable(a).map(A::getFoo).map(B::getBar).orElse(null);

Another alternative might be to try to access the innermost item, but I have a feeling that this is not considered good practice, either:

try {
    Bar bar = a.getFoo().getBar();
    ...
catch (NullPointerException e) {
    ...
}

Particularly, this will also catch any other NPEs after accessing that element -- either that, or you have to put only the Bar bar = ... in the try and everything else in another if block after the try, nullifying any (questionable) gains in readability or brevity.

Some languages have a Safe Navigation Operator, but it seems like Java is not one of them. This way, you could use a notation like a?.getFoo()?.getBar() != null, where a?.getFoo() will just evaluate to null if a is null. You could emulate behavior like this with a custom function and a lambda, though, returning an Optional or just a value or null if you prefer:

public static <T> Optional<T> tryGet(Supplier<T> f) {
    try {
        return Optional.of(f.get());
    } catch (NullPointerException e) {
        return Optional.empty();
    }
}

Optional<Bar> bar = tryGet(() -> a.getFoo().getBar(););

Tags:

Java

Null

Nullable

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