In this article, we’ll explore how to calculate the sum of the first N even numbers that are divisible by 3 in Java. We will start by providing a solution using a simple for loop, and then we’ll demonstrate an alternative solution using Java Streams.
1. Problem Definition
Given a number N, we need to find the sum of the first N even numbers that are divisible by 3. For example, if N = 7, the first seven even numbers are 0, 2, 4, 6, 8, 10, 12. From these, only the numbers 0, 6, 12 are divisible by 3, so the sum would be 0 + 6 + 12 = 18.
2. Using a for Loop
We can iterate through the first N even numbers, check if each one is divisible by 3, and then add it to the sum if it is. Here’s how we can implement this solution:
public class SumOfEvenNumbersDivisibleby3 {
public static void main(String[] args) {
int NUMBER = 7;
int result = sumOfEvenNumbersDivisibleBy3(NUMBER);
System.out.println("The sum of the first " + NUMBER + " even numbers divisible by 3 is: " + result);
}
public static int sumOfEvenNumbersDivisibleBy3(int N) {
int sum = 0;
for (int i = 0; i < N; i++) {
int num = i * 2;
if (num % 3 == 0) {
sum += num;
}
}
return sum;
}
}
In the above code example, the sumOfEvenNumbersDivisibleBy3 method begins by initializing a sum variable to 0. A for loop is used to iterate from i = 0 to i = N - 1, generating the even numbers by multiplying i by 2. For each even number, we check if it is divisible by 3 using num % 3 == 0. If the condition is true, the number is added to the sum. After the loop completes, the final sum of the even numbers divisible by 3 is returned.
In the main method, we set the variable NUMBER to 7, indicating that we want to find the sum of the first 7 even numbers divisible by 3. The method sumOfEvenNumbersDivisibleBy3(NUMBER) is then called, and its result is printed to the console.
Sample Output:
For NUMBER = 7, the output will be:
The sum of the first 7 even numbers divisible by 3 is: 18
3. Using Java Streams
The above solution uses a basic loop, but we can also implement this using Java Streams, which provides a more functional approach to processing sequences of data. Here is how we can implement the same solution using Streams:
public class StreamSumEvenNumbersDivisibleBy3 {
public static void main(String[] args) {
int NUMBER = 7;
int result = sumOfEvenNumbersDivisibleBy3(NUMBER);
System.out.println("The sum of the first " + NUMBER + " even numbers divisible by 3 is: " + result);
}
public static int sumOfEvenNumbersDivisibleBy3(int N) {
return IntStream.range(0, N)
.map(i -> i * 2)
.filter(num -> num % 3 == 0)
.sum();
}
}
In the sumOfEvenNumbersDivisibleBy3 method, we use IntStream.range(0, N) to generate a stream of numbers from 0 to N - 1, then apply map(i -> i * 2) to convert each number into its corresponding even number. The filter(num -> num % 3 == 0) step filters the stream to include only those numbers divisible by 3, and finally, .sum() computes the sum of the filtered numbers.
Sample Output:
For NUMBER = 7, the output will be the same as the previous solution:
The sum of the first 7 even numbers divisible by 3 is: 18
For NUMBER = 10, the first 10 even numbers are 0, 2, 4, 6, 8, 10, 12, 14, 16, 18. Among these, the numbers divisible by 3 are 0, 6, 12, 18. The sum of these numbers is 0 + 6 + 12 + 18 = 36.
Thus, the sample output for NUMBER = 10 would be:
4. Conclusion
In this article, we explored two approaches to calculating the sum of the first N even numbers divisible by 3 in Java. The first solution used a traditional for loop to iterate through the even numbers, check divisibility by 3, and sum the qualifying numbers. The second solution leveraged the power of Java Streams, providing a more concise and functional approach to achieve the same result.
5. Download the Source Code
This article explored how to calculate the sum of the first N even numbers that are divisible by three in Java.
You can download the full source code of this example here: Java sum first n even numbers divisible by three
