Convert Binary to Decimal using Recursion in Java

This article shows you how to convert Binary to Decimal using recursion in Java. Recursion in java is a technique in which a method calls itself continuously. A method in java that calls itself is called a recursive method.

How to convert binary to decimal?

Binary to Decimal conversion is straightforward, look into the below diagram for conversion in steps:

binary to decimal conversion in java

Java Program to Convert Binary to Decimal

Here, we will see two java programs for binary-to-decimal conversion using recursion in Java.

  1. Binary to Decimal – if the binary number is in integer format
  2. Binary to Decimal – if the binary number is in string format

Binary to Decimal using Recursion – if the binary number is in integer format

BinaryToDecimalRecursion.java

package com.javacodepoint.conversion;

/**
 * Binary to Decimal conversion using Recursion.
 */
public class BinaryToDecimalRecursion {

	// recursive method for binary to decimal
	public static int binaryToDecimal(int binary) {

		// if binary number become 0
		if (binary == 0) {
			return 0;
		}

		return (binary % 10 + 2 * binaryToDecimal(binary / 10));
	}

	// main method to test
	public static void main(String[] args) {

		// Binary number is in integer format
		System.out.println("Decimal Number of 1001 is: " + binaryToDecimal(1001));
		System.out.println("Decimal Number of 1111 is: " + binaryToDecimal(1111));
		System.out.println("Decimal Number of 1100110 is: " + binaryToDecimal(1100110));
		System.out.println("Decimal Number of 1000000001 is: " + binaryToDecimal(1000000001));
	}

}

OUTPUT:

Decimal Number of 1001 is: 9
Decimal Number of 1111 is: 15
Decimal Number of 1100110 is: 102
Decimal Number of 1000000001 is: 513

Binary to Decimal using Recursion – if the binary number is in string format

BinaryToDecimalRecursion2.java

package com.javacodepoint.conversion;

/**
 * Binary to Decimal conversion using Recursion.
 */
public class BinaryToDecimalRecursion2 {

	// recursive method for binary to decimal
	public static int binaryToDecimal(String binary, int i) {

		int length = binary.length();

		// if we reached to last character
		if (i == length - 1) {
			return binary.charAt(i) - '0';
		}

		// add current term and recursion for
		// remaining terms
		return ((binary.charAt(i) - '0') << (length - i - 1)) + binaryToDecimal(binary, i + 1);
	}

	// main method
	public static void main(String[] args) {

		// Binary number is in string format
		System.out.println("Decimal Number of 101 is: " + binaryToDecimal("101", 0));
		System.out.println("Decimal Number of 1010 is: " + binaryToDecimal("1010", 0));
		System.out.println("Decimal Number of 1111000 is: " + binaryToDecimal("1111000", 0));
		System.out.println("Decimal Number of 1000000001 is: " + binaryToDecimal("1000000001", 0));
	}

}

OUTPUT:

Decimal Number of 101 is: 5
Decimal Number of 1010 is: 10
Decimal Number of 1111000 is: 120
Decimal Number of 1000000001 is: 513

There are multiple ways for Binary to Decimal conversion also explained in another article, visit Java Binary to decimal conversion Program Examples.

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