从两个或多个不同长度的数组循环索引数组

Question

Hy, i want to make a method that gives me one array from three different arrays with different length indexing like:

[number of element in array][number of array]

[0][0],

[0][1],

[0][2],

[1][0],

[1][2]

So i made this:

    int a = 0;
    for (int i = 0; i < collections[a].length; i++) {
        for (int k = 0; k < collections.length; k++) {
            result[p] = collections[i][k];
            p++;
        }
    }

    return result;

but it only works when arrays are the same size and I have no idea what condition should be added to avoid "out of bounds" when it comes to from second element of the first array to second element of the third array excluding second element of the second array which does not even exist.

int[] array3 = { 10, 20, 30, };
int[] array4 = { 40, 50, };
int[] array5 = { 60, 70, 80, 90 };
A.method(array3, array4, array5);

and the result what i want to get is: 10,40,60,20,50,70,30,80,90

Answer 1

First, I find which array has the max length. Then I start two loops. The "outer" loop index j is used to access the individual arrays' elements, which I increment only after I've cycled through all the individual arrays once. I stop incrementing j once j has reached the max length calculated in first step.

private static int[] combine(int[]... arrays) {

    int maxArrayLen = Arrays.stream(arrays).mapToInt(array -> array.length).max().getAsInt();

    List<Integer> list = new ArrayList<Integer>();
    for (int j = 0; j < maxArrayLen; j++) {
        for (int i = 0; i < arrays.length; i++) {
            if (arrays[i].length > j) {
                list.add(arrays[i][j]);
            }
        }
    }
    return list.stream().mapToInt(i -> i).toArray();
}

To invoke this: combine(array3, array4, array5);

Running demo: https://ideone.com/F2yxKh