public static int beautifulTriplets(int d, List<Integer> arr) {
    int tripletcount = 0;
    for(int i = 0; i < arr.size(); i++) {
        for(int j=i+1; j< arr.size(); j++) {
            if(arr.get(j) - arr.get(i) == d && findThirdNumber(arr, j, d, arr.get(j))) {
                tripletcount++;
                break;
            }
        }
    }
    return tripletcount;
}

private static boolean findThirdNumber(List<Integer> arr, int j, int d, int jval) {
    for(int k = j+1; k < arr.size(); k++) {
        if(arr.get(k) - jval == d) return true;
    }
    return false;
}