public static int[] k_merge(ArrayList<int[]> k_array) {
    if(CollectionUtils.isEmpty(k_array)){
        return new int[0];
    }
    int size = k_array.size();
    int k = size;
    ArrayList<int[]> objects = null;
    while (k > 1) {
        objects = Lists.newArrayList();
        for (int i = 0; i < k; i += 2) {
            if (i + 1 < k) {
                int[] ints = m_merge(k_array.get(i), k_array.get(i + 1));
                objects.add(ints);
            } else {
                objects.add(k_array.get(i));
            }
        }
        k_array.clear();
        for(int i=0;i<objects.size();i++){
            k_array.add(objects.get(i));
        }
        k = k_array.size();
    }
    return objects.get(0);
}

public static int[] m_merge(int[] a, int[] b) {
    int a_length = a.length;
    int b_length = b.length;
    int[] result = new int[a_length + b_length];
    int lpos = 0;
    int rpos = 0;

    for (int i = 0; i < result.length; i++) {
        if (lpos < a_length && rpos < b_length) {
            if (a[lpos] <= b[rpos]) {
                result[i] = a[lpos++];
            } else {
                result[i] = b[rpos++];
            }
        } else if (lpos < a_length) {
            result[i] = a[lpos++];
        } else if (rpos < b_length) {
            result[i] = b[rpos++];
        }
    }
    return result;
}