Java program to calculate the power using recursion

To calculate the power of a number, Java provides different ways to do this using loops, built-in methods, and recursion. In this article, we will learn how to calculate the power of a number using recursion.

In Java, Recursion is a process in which a function calls itself multiple times until it reaches a base condition, and the corresponding function is called a recursive function.

Problem Statement

Given a base number and a power value, we need to calculate the result of raising the base to the power using recursion. Below is a demonstration of the same.

Input: Enter the number and its power 2 and 5
Output: The result of 2^5 is 32

Calculating the Power Using Recursion

Below are the different ways to calculate the power using recursion.

• Using user-defined input
• Using predefined input

Using user-defined input

Following are the steps to calculate the power using recursion based on user-defined input.

• Import the Scanner class from the java.util package to handle user input.

• Define a class (e.g., PowerUsingRecursion) that contains the main method and the recursive method.

• Create a method that uses recursion to calculate the power by repeatedly multiplying the base number until the exponent reaches zero.

• Create a recursive method that checks if the exponent is 0. If so, return 1 as the base case. Otherwise, return base * power(base, exponent - 1).

• Pass the user inputs to the recursive method to compute the power of the base raised to the exponent.

• Display the output.

Example

Here, the input is being entered by the user based on a prompt -

import java.util.Scanner;
public class PowerUsingRecursion {
   // Recursive method to calculate base^exponent
   public static int power(int base, int exponent) {
      if (exponent == 0) {
         return 1; // Base case
      }
      return base * power(base, exponent - 1); // Recursive case
   }
   public static void main(String[] args) {
      Scanner scanner = new Scanner(System.in);
      // Taking input from user
      System.out.print("Enter the base: ");
      int base = scanner.nextInt();
      System.out.print("Enter the exponent: ");
      int exponent = scanner.nextInt();
      // Call the recursive method
      int result = power(base, exponent);
      // Display the result
      System.out.println(base + " raised to the power " + exponent + " is: " + result);
   }
}

Output

Enter the base: 2
Enter the exponent: 3
2 raised to the power 3 is: 8

Using Predefined Values

Following are the steps to calculate the power using recursion based on user-defined input.

• Declare and initialize integer variables for base and exponent.

• Create a method named power() that returns 1 when the exponent is 0 (base case), and otherwise returns base * power(base, exponent - 1).

• Pass the defined base and exponent values to the recursive method to compute the power of the base raised to the exponent.

• Display the output.

Example

Here, the integer has been previously defined, and its value is accessed and displayed on the console.

public class PowerUsingRecursion {
   // Recursive method to calculate power
   public static int power(int base, int exponent) {
      if (exponent == 0) {
         return 1; // Base case
      }
      return base * power(base, exponent - 1); // Recursive step
   }
   public static void main(String[] args) {
      int base = 3; // base value defined directly
      int exponent = 4; // exponent value defined directly
      int result = power(base, exponent); // calling recursive method
      System.out.println(base + " raised to the power " + exponent + " is: " + result);
   }
}

Output

3 raised to the power 4 is: 81