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;
        }
        return total > num;
    }
}

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));
        }
    }
}
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