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BAEL-8295 Sum of first n even numbers divisible by 3 #17761

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Merged
merged 4 commits into from
Oct 14, 2024
Merged

BAEL-8295 Sum of first n even numbers divisible by 3 #17761

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881412f
BAEL-8295 Sum of first n even numbers divisible by 3
yabetancourt Oct 4, 2024
da84d9a
BAEL-8295 Refactor algorithms
yabetancourt Oct 6, 2024
312ee78
BAEL-8295 removed public modifier from unit tests
yabetancourt Oct 9, 2024
5171754
BAEL-8295 removed white spaces
yabetancourt Oct 10, 2024
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54 changes: 54 additions & 0 deletions .../java/com/baeldung/sumofnevendivisibleby3/SumOfNFirstEvenNumbersDivisibleBy3UnitTest.java
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package com.baeldung.sumofnevendivisibleby3;

import org.junit.jupiter.api.Test;

import java.util.stream.IntStream;

import static org.junit.jupiter.api.Assertions.assertEquals;

class SumOfNFirstEvenNumbersDivisibleBy3UnitTest {

private static final int NUMBER = 7;
private static final int EXPECTED_SUM = 18;

@Test
void givenN_whenUsingBruteForceForLoop_thenReturnsCorrectSum() {
int sum = 0;

for (int i = 2; i <= NUMBER * 2; i++) {
if (i % 2 == 0 && i % 3 == 0) {
sum += i;
}
}

assertEquals(EXPECTED_SUM, sum);
}

@Test
void givenN_whenUsingFunctionalApproach_thenReturnsCorrectSum() {
int sum = IntStream.iterate(2, i -> i + 1)
.filter(i -> i % 2 == 0)
.limit(NUMBER)
.filter(i -> i % 3 == 0)
.sum();

assertEquals(EXPECTED_SUM, sum);
}

@Test
void givenN_whenUsingImprovedBruteForce_thenReturnsCorrectSum() {
int sum = IntStream.iterate(6, i -> i + 6)
.limit(NUMBER / 3)
.sum();

assertEquals(EXPECTED_SUM, sum);
}

@Test
void givenN_whenUsingOptimizedMethod_thenReturnsCorrectSum() {
int sum = 3 * (NUMBER / 3) * (NUMBER / 3 + 1);

assertEquals(EXPECTED_SUM, sum);
}

}