Java Community | Help. Code. Learn.•2y ago

Intellij is complaining about this code, not sure why

    public K get(int i) {
        int j = 0;
        this.forEach((K key, V value) -> {
            if (j == i) {
                return key;
            }
            j++;
        });
        return null;
    }

    public K get(int i) {
        int j = 0;
        this.forEach((K key, V value) -> {
            if (j == i) {
                return key;
            }
            j++;
        });
        return null;
    }

its saying "variable used in lambda expression should be final or effectively final" (about j), and gives the option to convert j to atomic. Im wondering what that means, and what atomic is. (K and V are generics, this class extends HashMap)

9 Replies

JavaBot•2y ago

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Kyo-chan•2y ago

Inside a lambda, you can't reassign a local variable that was declared outside of that lambda. Here you're reassigning j in the lambda, despite it's a local variable declared in get(). That doesn't work IntelliJ offers to replace with an AtomicInteger, because then you wouldn't need to reassign it. You would just need to call a method to update it. That is, however, a hacky solution that shouldn't be used. In your case, that wouldn't even solve the entire problem Indeed, you're trying to return from inside the lambda, which can't be done either Your better bet is to get rid of the lambda altogether, and to iterate over the Map's entries instead.

blockgoblin31OP•2y ago

Im not sure how to do that

Kyo-chan•2y ago

for(Map.Entry<K, V> entry : this.entrySet()) {

for(Map.Entry<K, V> entry : this.entrySet()) {

(Come to think of it, the better solution is to stream the keys, skip i-1 of them, and return the first found in the rest)

blockgoblin31OP•2y ago

something like this?

        for (K key : this.keySet()) {
            if (j == i) return key;
            j++;
        }

        for (K key : this.keySet()) {
            if (j == i) return key;
            j++;
        }

Kyo-chan•2y ago

Yeah, it's even better

blockgoblin31OP•2y ago

cool, thanks

JavaBot•2y ago

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Intellij is complaining about this code, not sure why