Check Map not to contain null keys and values

Question

For now I have this ugly code to check whether a hashmap contains null keys and values. Is there ready to use Guava static method with same functionality?

    if (map != null) {
        // Check map does not contains null key
        try {
            if (map.containsKey(null)) {
                throw new IllegalArgumentException("map contains null as key");
            }
        } catch (NullPointerException e) {
            //It is ok. Map does not permit null key.
        }

        // Check map does not contains null key
        try {
            if (map.containsValue(null)) {
                throw new IllegalArgumentException("map contains null price");
            }
        } catch (NullPointerException e) {
            //It is ok. Map does not permit null value.
        }
    }

Easy, efficient and elegant way to check whether a give map contains no null elements (keys and values) — Nikolay Kuznetsov, Feb 12 '14 at 20:01

score 1 · Answer 1 · edited May 23 '17 at 12:21

Not really. There's

Preconditions.checkNotNull

which you should probably use. Surprisingly, it's faster than your simple check (it's optimized for better inlining of the common case, i.e., not throwing). It throws NPE instead of IAE.

There are also MapConstraints, which AFAIK would allow you to create such a Map.

And there are also many classes not allowing nulls, e.g., ImmutableMap. In theory you could do

ImmutableMap.copyOf(map)

but this would needlessly create a copy.

score 0 · Answer 2 · answered Feb 06 '14 at 00:33

0

If you can use an ImmutableMap from the beginning, perhaps via its Builder, you'd get an error as soon as you tried to insert a null key or value. So that might be worth a look.

answered Feb 06 '14 at 00:33

isomeme

451
3
12

score 0 · Answer 3 · answered Feb 06 '14 at 16:41

This is simple enough:

public static <K,V>boolean containsNullKeysOrValues(Map<K,V> map){
    return containsNullKeys(map)|| containsNullValues(map);
}
public static <K, V> boolean containsNullKeys(Map<K, V> map) {
    return Iterables.tryFind(map.keySet(), Predicates.isNull()).isPresent();
}
public static <K, V> boolean containsNullValues(Map<K, V> map) {
    return Iterables.tryFind(map.values(), Predicates.isNull()).isPresent();
}

Pro: You don't have to catch any NPEs.

Con: In the worst case you have to iterate the entire map. Twice.

Check Map not to contain null keys and values

3 Answers3