inbuild method to sum of an arraylist elements in java

1int total = numbers.stream().mapToInt(i -> i.intValue()).sum();
2		System.out.print(total);

1doubleList.stream().reduce((a,b)->a+b).get();
2

1//If you have a List<Integer>
2int sum = list.stream().mapToInt(Integer::intValue).sum();
3
4//If it's an int[]
5int sum = IntStream.of(a).sum();