Java Program to Convert Decimal to Binary By Using Recursion

Prerequisite: Recursion in Java

In the previous article, we have discussed about Java Program to Reverse an Array by Using Recursion

In this program we are going to see how to convert decimal to binary using Recursion by Java programming language.

Java Program to Convert Decimal to Binary Using Recursion

Lets assume there is a decimal number A = 786

So the binary of 786 = 1100010010

Now let’s see different ways to convert decimal to binary by using Recursion.

By Using Static Input and Recursion
By Using User Input and Recursion

Method-1: Java Program to Convert Decimal to Binary By Using Static Input and Recursion

Approach:

Declare and initialize an integer variable say ‘dec’
Call a user defined method calculateBin() and pass the ‘dec’ as parameter.
Inside the user defined method, check if the decimal number is zero or not. If the decimal number is 0 then return 0 else call the same method as “(dec%2) + (10*(calculateBin(dec/2)))” and return the value to the main method.
Now the value of the user defined method calculateBin() is stored in an integer variable say ‘bin’.
Print the value of binary number.

Program:

import java.util.*;
import java.io.*;
public class Main 
{
    public static void main(String[] args)
    {
        //declare and initialize an integer variable dec
        int dec = 786;
        //call the method and store the value inside an integer variable say ‘bin’
        int bin = calculateBin(dec);
        //print the result
        System.out.println("The binary form of the decimal number "+dec+" is: "+bin);
    }
    
    //calculateBin() method to convert decimal to binary
    static int calculateBin(int dec)
    {
        if (dec == 0)
         return 0;
        else
         return (dec%2) + (10*(calculateBin(dec/2)));
    }
}

Output:

The binary form of the decimal number 786 is: 1100010010

Method-2: Java Program to Convert Decimal to Binary Using Recursion By Using User Input and Recursion

Approach:

Create a scanner class object.
Declare an integer variable say ‘dec’
Prompt the user to enter a decimal number.
Call a user defined method calculateBin() and pass the ‘dec’ as parameter.
Inside the user defined method, check if the decimal number is zero or not. If the decimal number is 0 then return 0 else call the same method as “(dec%2) + (10*(calculateBin(dec/2)))” and return the value to the main method.
Now the value of the user defined method calculateBin() is stored in an integer variable say ‘bin’.
Print the value of binary number.

Program:

import java.util.*;
import java.io.*;
public class Main 
{
    public static void main(String[] args)
    {
        // create a scanner class
        Scanner s = new Scanner(System.in);
        System.out.println("Enter a decimal number:");
        //declare an integer variable ‘dec’and initialize it by user input using scanner class.
        int dec = s.nextInt();
        //define the method and store the value inside an integer variable say ‘bin’
        int bin = calculateBin(dec);
        //print the result
        System.out.println("The binary form of the decimal number "+dec+" is: "+bin);
    }
    
    static int calculateBin(int dec)
    {
        if (dec == 0)
         return 0;
        else
         return (dec%2) + (10*(calculateBin(dec/2)));
    }
}

Output:

Enter a decimal number:
17
The binary form of the decimal number 17 is: 10001

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