# Excessively Abundant Numbers in Java

## The challenge

An abundant number or excessive number is a number for which the sum of its proper divisors is greater than the number itself.

The integer 12 is the first abundant number. Its proper divisors are 1, 2, 3, 4 and 6 for a total of 16 (> 12).

Derive function `abundantNumber(num)/abundant_number(num)` which returns `true/True/.true.` if `num` is abundant, `false/False/.false.` if not.

## The solution in Java code

Option 1 (using `IntStream`):

``````import java.util.stream.IntStream;

public class Solution {
public static boolean abundantNumber(int num) {
return num < IntStream.rangeClosed(1, num/2).filter(i -> num % i == 0).sum();
}
}
``````

Option 2 (without using streams):

``````public class Solution {
public static boolean abundantNumber(int num) {
int total = 0;
for(int i=1;i<(num/2)+1;i++){
if(num%i==0) total += i;
}
}
}
``````

## Test cases to validate our Java solution

``````import org.junit.Test;
import static org.junit.Assert.assertEquals;
import java.util.Random;

public class AbundantTests {
@Test
public void testAbundant() {
assertEquals("Should work with 12", true, Solution.abundantNumber(12));
assertEquals("Should work with 18", true, Solution.abundantNumber(18));
assertEquals("Should work with 120", true, Solution.abundantNumber(120));
assertEquals("Should work with 5830", true, Solution.abundantNumber(5830));
assertEquals("Should work with 11410", true, Solution.abundantNumber(11410));
assertEquals("Should work with 11690", true, Solution.abundantNumber(11690));
}

@Test
public void testNonAbundant() {
assertEquals("Should return false with 37", false, Solution.abundantNumber(37));
assertEquals("Should return false with 77", false, Solution.abundantNumber(77));
assertEquals("Should return false with 118", false, Solution.abundantNumber(118));
assertEquals("Should return false with 14771", false, Solution.abundantNumber(14771));
}

private static boolean abundantNumber(int num) {
int sum = 0;
for (int i = 1; i <= Math.sqrt(num); i++) {
if (num % i == 0) {
sum += i;
if (i != num / i) {
sum += num / i;
}
}
}
return (sum - num > num);
}

@Test
public void testRandomNumbers() {
Random random = new Random();
for(int i = 0; i < 40; i++) {
int num = random.nextInt(99000) + 1000;
assertEquals("Failed on random test: " + num, abundantNumber(num), Solution.abundantNumber(num));
}
}
}
``````