# Get the Sum of Digits / Digital Root using Java ## The challenge

Digital root is the recursive sum of all the digits in a number.

Given `n`, take the sum of the digits of `n`. If that value has more than one digit, continue reducing in this way until a single-digit number is produced. This is only applicable to the natural numbers.

### Examples

```    16  -->  1 + 6 = 7
942  -->  9 + 4 + 2 = 15  -->  1 + 5 = 6
132189  -->  1 + 3 + 2 + 1 + 8 + 9 = 24  -->  2 + 4 = 6
493193  -->  4 + 9 + 3 + 1 + 9 + 3 = 29  -->  2 + 9 = 11  -->  1 + 1 = 2
```

## Tests cases

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

public class DRootExampleTest {
@Test
public void Tests() {
assertEquals( "Nope!" , 7, DRoot.digital_root(16));
assertEquals( "Nope!" , 6, DRoot.digital_root(456));
}
}
```

## The solution in Java

```public class DRoot {
public static int digital_root(int n) {

// return the number if less than 10
// this is to break out of the recursion loop
if (n<10) return n;

// set an output variable
int out = 0;

// while we still have numbers, loop
while(n>0) {
// increment our output by the base
out += n % 10;
// reduce the base by the same amount
n = n / 10;
}

// return a recursion of the output
return digital_root(out);
}
}

```
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