How do you find the sum of all numbers in a set in Java? [duplicate]

问题

This question already has answers here:

Is there possibility of sum of ArrayList without looping (13 answers)

Closed 1 year ago.

How would you find the sum of the elements of a set in Java? Would it be the same with an array?

In python, I could do:

my_set = {1, 2, 3, 4} 
print(sum(my_set)) 

回答1:

Aside from using loops explicitly, for List<Integer> list you can do:

int sum = list.stream().mapToInt(Integer::intValue).sum();

If it's an int[] ar then do:

int sum = IntStream.of(ar).sum();

This is based on the use of streams.

Or you can do this simple one liner loop:

int sum = 0;
for (Integer e : myList) sum += e;

Even better, write a function and reuse it:

public int sum(List<Integer> list) {
    int sum = 0;
    for (Integer e : list) sum += e;

    return sum;
}

回答2:

int sum = 0;
for( int i : my_set) {
    sum += i;
}

System.out.println(sum);

回答3:

Here is simple example to get sum of list elements.

 public static void main(String args[]){
      int[] array = {10, 20, 30, 40, 50};
      int sum = 0;
      for(int num : array) {
          sum = sum+num;
      }
      System.out.println("Sum of array elements is:"+sum);
   }

Output :

Sum of array elements is:150

Hope this solution helpful you to understand the concept.

来源：https://stackoverflow.com/questions/58811850/how-do-you-find-the-sum-of-all-numbers-in-a-set-in-java