# How to Find the Mean/Average of a List of Numbers in Java ## The challenge

Find the mean (average) of a list of numbers in an array.

To find the mean (average) of a set of numbers add all of the numbers together and divide by the number of values in the list.

For an example list of `1, 3, 5, 7`

1. Add all of the numbers

```1+3+5+7 = 16
```

2. Divide by the number of values in the list. In this example there are 4 numbers in the list.

```16/4 = 4
```

3. The mean (or average) of this list is 4

## Test cases

```import static org.junit.Assert.*;
import org.junit.Test;

public class AveragerTest {
@Test
public void test1() {
assertEquals(1,
Averager.findAverage(new int[]{1}));
}
@Test
public void test2() {
assertEquals(4,
Averager.findAverage(new int[]{1,3,5,7}));
}
}
```

## Find the Mean/Average in Java

Avoid performing a for loop, in favour of an `Arrays.stream`:

```import java.util.*;
public class Averager {

public static int findAverage(int[] nums) {
// sum all the elements and divide by the amount of elements
return Arrays.stream(nums).sum()/nums.length;
}
}
```

Alternatively, use the `average` functional directly and avoid summing and dividing by the length:

```import java.util.Arrays;

public class Averager {

public static int findAverage(int[] nums) {
// or use the internal `average`
return (int)Arrays.stream(nums).average().orElse(0);
}
}
```

Another great option is to use the `summaryStatistics` extension of the `InStream` class to then in turn use the `getAverage` method as follows:

```import java.util.stream.IntStream;
public class Averager {

public static int findAverage(int[] nums) {
// or explore the `summaryStatistics` route
return (int)IntStream.of(nums).summaryStatistics().getAverage();
}
}
```

If all else fails, there’s always good old faithful, using a for loop:

```public class Averager {

public static int findAverage(int[] nums) {
int sum = 0;
for (int num : nums) {
sum += num;
}
return sum / nums.length;
}
}
```
Tags:
0 0 vote
Article Rating
Subscribe
Notify of 