Java 8

public static void bonAppetit(List bill, int k, int b) { // Write your code here

    int totalCost = bill.stream().mapToInt(Integer::intValue).sum();
    int splitCharge = (totalCost - bill.get(k)) / 2;
    if(b - splitCharge > 0){
        System.out.println(b - splitCharge);
    } else{
        System.out.println("Bon Appetit");
    }

}

Here is my c++ solution you can find the video here : https://youtu.be/MHFroRIBGQc

void bonAppetit(vector<int> bill, int k, int b) {
    int s = accumulate(bill.begin(), bill.end(), -1 * bill[k]);
    int c = s / 2;
    if(c == b) cout << "Bon Appetit";
    else cout << b - c;
}

java(8)

public static void bonAppetit(List<Integer> bill, int k, int b) {
    // Write your code here
    int billAnna = 0;
    int billSum = 0;
    for (int i : bill) {
        billSum += i;
    }

    int billSplit = billSum / 2;

    if (billSplit == b) {
        for (int i = 0; i < bill.size(); i++) {
            if (i == k) {
                continue;
            }
            billAnna += bill.get(i);

        }

        System.out.println((b - (billAnna / 2)));
    } else {
        System.out.println("Bon Appetit");
    }

}