Recursion

Recursion is a technique where a method calls itself to solve a problem. It's often used to break down complex problems into simpler versions of themselves.

How It Works

Every recursive method needs two parts:

1. Base Case: The condition to stop calling itself (otherwise, it loops forever and crashes).
2. Recursive Case: The part where the method calls itself with a modified parameter (moving towards the base case).

int factorial(int n) {
    if (n == 1) {
        return 1; // Base Case: Stop!
    } else {
        return n * factorial(n - 1); // Recursive Step
    }
}

Example: Mathematical Factorial

The factorial of 5 (written as 5!) is 5 * 4 * 3 * 2 * 1.

• factorial(5) returns 5 * factorial(4)
• factorial(4) returns 4 * factorial(3)
• ...and so on, until factorial(1) returns 1.

Click Run to execute your code

Stack Overflow Error

If you forget the Base Case, the method keeps calling itself infinitely until the computer runs out of memory. In Java, this throws a StackOverflowError.

// BAD CODE (Crashes)
int badMethod(int n) {
    return n * badMethod(n - 1); // No stopping condition!
}

Summary