List<Integer> list = new ArrayList<>();
for (int i = 1; i<1001; i++){
    int sum = 0;
    for(int a=i; a>0; a/=10){
        sum += (a%10)*(a%10);
    }
    if (sum%2==0) list.add(i);
}

List<Integer> list = IntStream.range(1, 1000)
            .filter(number -> Math.sqrt(number) % 1 == 0)
            .boxed()
            .collect(Collectors.toList());