How can i get around this?

Question

I have this piece of code and i dont understand why I m getting the following error:

local variables referenced from a lambda expression must be final or effectively final

Here is my code

    public int firstMissingPositive(int[] nums) {

        int k;

        for (int i = 1;; i++) {
            if (!Arrays.stream(nums).anyMatch(x -> x != i)) {
                k = i;
                break;
            }
        }
        return k;
    }

If you typed *local variables referenced from a lambda expression must be final or effectively final* or some combination of it, SO would have shown you several duplicates. — achAmháin, Nov 06 '18 at 17:26
The code has very bad performance (_O(n^2)_). You can get better performance by either sorting the array, or by building a `boolean[]` of found values, or ... — Andreas, Nov 06 '18 at 17:35
For the future: please spend some time to find a *reasonable* title for your question. This is a Q/A community, all content should be written to be helpful for future readers. Few future readers will find *How can i get around this?* to be a helpful starting point ... — GhostCat, Nov 07 '18 at 15:35

score 3 · Accepted Answer · answered Nov 06 '18 at 17:28

3

Because i is not effectively final (see i++), and it must be to be used in a lambda expression.

It is easy enough to fix, by assigning to a new local variable inside the loop:

public int firstMissingPositive(int[] nums) {
    int k;
    for (int i = 1;; i++) {
        final int j = i;
        if (! Arrays.stream(nums).anyMatch(x -> x != j)) {
            k = j;
            break;
        }
    }
    return k;
}

answered Nov 06 '18 at 17:28

Andreas

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this should also work without final keyword for `j` right? – Ryuzaki L Nov 06 '18 at 17:33
1

@Deadpool Yes. It's "effectively final" even without the keyword. – Michael Nov 06 '18 at 17:34
sounds good @Michael – Ryuzaki L Nov 06 '18 at 17:36

How can i get around this?

1 Answers1