Calculate Number Series Total

Ever wondered how to quickly find the total sum of all numbers from 1 up to a certain value? Whether it’s for a math problem, a leaderboard calculation, or just good practice, you can easily do this in Apex with a simple loop.

In this post, we’ll create an Apex method that accepts a number and returns the sum of all integers from 1 up to that number. If you’re learning Apex and want to build your confidence with loops and logic, this one’s a great place to start!

🧠 What Are We Trying to Do?

Let’s say we call the method with the input 5.

We want to calculate:

1 + 2 + 3 + 4 + 5 = 15

The method should:

• Accept a final number

• Loop from 1 to that number

• Add each number to a total

• Return the total at the end

This is also a great introduction to for-loops and accumulation logic in Apex.

🔍 Code Explanation

public with sharing class ApexUseCaseSixteen {
    
    public static Integer sumOfAll(Integer finalNumber){

We define a class called ApexUseCaseSixteen and create a static method sumOfAll that takes one input: the number we want to sum up to.

        Integer totalSum = 0;

We initialize a variable totalSum to 0. This is where we’ll store our running total.

        for(Integer i = 1; i <= finalNumber; i++){
            totalSum += i;
        }

Here’s the loop:

• We start from 1 and go up to (and including) finalNumber

• On each loop, we add i to totalSum using the shorthand +=

This way, the method adds 1 + 2 + 3 + … until it reaches the number we passed in.

        return totalSum;
    }
}

Finally, we return the sum back to the caller.

✅ Why This Is Useful

This small method packs a lot of learning:

• It teaches for-loops

• Shows how to build running totals

• Gives real-world value in areas like:

  • Scores and points

  • Total prices

  • Task counters

  • Any place where cumulative sums matter

Want to level it up?

• You could skip the loop and use the formula: n(n + 1)/2 for instant results

• Add input validation (like if the number is less than 1)

• Return the total as a string with a message

🧾 Final Code Snippet

public with sharing class ApexUseCaseSixteen {
    
    public static Integer sumOfAll(Integer finalNumber){
        Integer totalSum = 0;
        for(Integer i = 1; i <= finalNumber; i++){
            totalSum += i;
        }
        return totalSum;
    }
}

🎥 Watch It in Action!

Prefer watching instead of reading? I’ve created a short demo where I run this method inside the Developer Console and explain each step visually.