Print the sum of corresponding elements in two arrays

Question

In this exercise, I'm supposed to sum up elements from 2 arrays, then display the answer on one line with spaces in between. I did it and my answer got accepted as correct, but I'm wondering if there is a better way to do this since I feel my way was more complicated than it needed to be.

import java.util.ArrayList;
import java.util.List;

public class Main {

public static void main(String[] args) {
    int n = 11;

    int[] firstArray = {811594, 993574, 299729,559604,161945,969851,588210,
            692459, 28350,43017,797855};
    int[] secondArray = {725888, 233750,191700,944750,380402,319860,766872,764921,
            330218,906679, 65309};

    List<Object> total = new ArrayList<>();

    for(int i = 0; i < n; i++){
        int sum = firstArray[i] + secondArray[i];
        total.add(sum);
    }

    Integer[] sumArray = total.toArray(new Integer[total.size()]);
    for(int i = 0; i < n; i++) {
        System.out.print(sumArray[i] + " ");
    }


}
}

Answer 1

You don't need to store the intermediate result. You don't need to give the length of the arrays. This assumes that the arrays are allways of equal length.

for(int i = 0; i < firstArray.length; i++){
    System.out.print((firstArray[i] + secondArray[i]) + " ");
}

Answer 2

@Orden is right that you don't need an intermediary array. On top of that, I would point out a few violations of good practices.

Use the right types. If you want to add integers in a list, then use a List<Integer> instead of a List<Object>.

If you know the final size of the list in advance, and you intend to convert it to an array, then consider skipping the list completely, and use just an array from the start. Like this:

int[] sumArray = new int[n];

for(int i = 0; i < n; i++){
    sumArray[i] = firstArray[i] + secondArray[i];
}

Answer 3

The basic idea is right, but I don't like this line and its consequences:

List<Object> total = new ArrayList<>();

• If you just need to print the result, you don't need to store the sums at all; you can just print as you go.
• If you want to store the sums, and you know the lengths of the inputs, then you can just make an array instead of an ArrayList to help you do it.
• If you do use an ArrayList, then providing a capacity estimate would be good practice.
• List<Object> defeats type safety. List<Integer> would be better.

Also, instead of hard-coding n = 11;, I suggest

assert firstArray.length == secondArray.length;
int n = firstArray.length;

---

So, one good solution would be

for (int i = 0; i < n; i++) {
    System.out.print((firstArray[i] + secondArray[i]) + " ");
}
System.out.println();     // It's customary to finish with a newline

Another good solution would be

int[] sums = new int[n];
for (int i = 0; i < n; i++) {
    sums[i] = firstArray[i] + secondArray[i];
}
for (int i = 0; i < n; i++) {
    System.out.print(sums[i] + " ");
}
System.out.println();

Answer 4

Others have covered bad practices here, I am just going to demonstrate a Java 8 solution to the problem - as Java 8 is the current version of Java; I believe this is what should be written in modern Java:

assert firstArray.length == secondArray.length;
IntStream.range(0, firstArray.length)
    .map(i -> firstArray[i] + secondArray[i])
    .forEach(System.out::println);

This simply creates an IntStream of [0, n) and then uses those indices to map to the sum of the variables.

Answer 5

The "modern" java solution puts newlines, not spaces between the elements, of course. Adding the trailing space, and using print instead of println will fix that. Inserting a join (Java has join, right?) might also work.

And, whats' wrong with APL's ⎕←firstArray+secondArray