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Learn Data Structures and Algorithms in Java

Recursion vs. Iteration

Explore the key distinctions between recursion and iteration by solving the same problem both ways. Understand advantages in readability, performance, and memory usage. Learn when to prefer simple loops versus recursive techniques based on problem structure and input size.

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In the previous lesson, recursion was introduced as a technique where a method calls itself with a smaller input until it reaches a base case. This raises an important question: if loops can already handle repetition, what advantages does recursion provide? Conversely, why is recursion not always the preferred approach?

The answer is that recursion and iteration are two different tools, and knowing when to reach for each one is an important skill. In this lesson, we will solve the same problem both ways, compare the two approaches, and build an intuition for when each one is the right choice.

Two ways to solve the same problem

Let's use factorial again as we are already familiar with it. Recall that 5! = 5 × 4 × 3 × 2 × 1 = 120.

Iterative approach

An iterative solution uses a loop to multiply the numbers together one by one, building up the result step by step.

Java 25
public class Main {
    public static int factorialIterative(int n) {
        int result = 1;
        for (int i = 1; i <= n; i++) {
            result *= i;
        }
        return result;
    }
    public static void main(String[] args) {
        System.out.println(factorialIterative(5));  // Output: 120
        System.out.println(factorialIterative(3));  // Output: 6
        System.out.println(factorialIterative(0));  // Output: 1
    }
}

The loop starts at 1 and multiplies up to n, ...