Commit 92dd726

<title>Recursion in Java</title>

<introduction>

</introduction>

<section xml:id="basic-recursion">

<title>Basic Recursion</title>

<p>

In this chapter, we will explore how to translate your recursive logic from Python to Java. While the core concepts of recursion remain the same, the syntax and structure of your code will change somewhat.

</p>

<p><idx>recursion</idx>

As you may know from Python, <term>recursion</term> is a powerful problem-solving technique involving base cases and recursive steps in which a function or method calls itself. When moving to Java, the core logic you've learned remains identical. The challenge is adapting that logic to Java's statically-typed, class-based syntax.

Let's take the familiar factorial function (which calculates the factorial of a number, namely the product of all positive integers from 1 to n). The logical steps in the code are the same, but the implementation details change.

# Let's calculate the factorial of 5.

x = 5

print("The factorial of " + x + " is: " + result)

The Java version follows the same recursive logic but requires three key syntax changes: the method must be inside a class, you must declare the parameter and return types (<c>int n</c> and <c>int return</c>), and you use <c>public static</c> to make it callable from <c>main</c>. The base case and recursive step remain conceptually identical.

</p>

<p>

Here is the equivalent Java code:

<program interactive="activecode" language="java">

// Let's calculate the factorial of 5.

int x = 5;

int result = Main.factorial(x); // Call the existing factorial method.

// Print the result.

System.out.println("The factorial of " + x + " is: " + result);

<title>Common Recursive Patterns</title>