Recursion in Java

This article explains about recursion in Java. We will learn what is recursion and how to use recursion to write effective Java programs.

Recursion is a famous way to solve problems with less lines of code. Many programmers prefer recursion over iteration as less amount of code is required to solve problems using recursion.

A method calling itself in its definition (body) is known as recursion. For implementing recursion, we need to follow the below requirements:

• There should be a base case where the recursion terminates and returns a value.
• The value of the parameter(s) should change in the recursive call. Otherwise, this leads to infinite loop.

Let’s consider the code for finding factorial of a number using iteration as shown below:

int fact(int n)
{
   int r = 1;
   for(int i = n; i > 1 ; i--)
   {
      r = i * r;
   }
   return r;
}

Now, let’s consider the recursive solution for finding the factorial of a given number which is shown below:

int rfact(int n)
{
   if(n == 0 || n == 1)
      return 1;
   else
      return n * rfact(n-1);  //recursive call
}

The complete Java program which demonstrates recursion is given below:

class RecursionDemo
{
	public static void main(String[] args)
	{
		int n = 6;
		System.out.println("Factorial of " + n + " without recursion is: " + fact(n));
		System.out.println("Factorial of " + n + " using recursion is: " + rfact(n));
	}
	static int fact(int n)
	{
		int r = 1;
		for(int i = n; i > 1 ; i--)
		{
			r = i * r;
		}
		return r;
	}
	static int rfact(int n)
	{
		if(n == 0 || n == 1)
			return 1;
		else
			return n * rfact(n-1);  //recursive call
	}
}

Suryateja Pericherla

Suryateja Pericherla, at present is a Research Scholar (full-time Ph.D.) in the Dept. of Computer Science & Systems Engineering at Andhra University, Visakhapatnam. Previously worked as an Associate Professor in the Dept. of CSE at Vishnu Institute of Technology, India.

He has 11+ years of teaching experience and is an individual researcher whose research interests are Cloud Computing, Internet of Things, Computer Security, Network Security and Blockchain.

He is a member of professional societies like IEEE, ACM, CSI and ISCA. He published several research papers which are indexed by SCIE, WoS, Scopus, Springer and others.