Program to convert binary number to decimal (java api, iterative & recursive)

• Given a binary number, convert binary number to decimal number using java.
• We discuss various methods to convert binary number to decimal.
  1. Convert binary to decimal using Integer class
     • Integer.parseInt method by specifying base 2.
  2. Iterative program to convert binary number to decimal number.
  3. Recursive program to convert binary number to decimal number.

Let us look into different methods to convert binary number to decimal number in java.

Method 1: Convert binary number to decimal in java (Integer.parseInt)

//binaryNumber = "1010"
private static int toDecimalUsingParseInt(String binaryNumber) {
        //output: decimal = 10
	return Integer.parseInt(binaryNumber, 2);
}

Method 2: Convert binary number to decimal in java (iterative method)

• Let us assume input binary number is “1010”.
• Binary to decimal conversion is :2³ * 1 + 2² * 0 + 2¹ * 1 + 2⁰ * 0 = 10
• Program to convert binary to decimal number is as follows:

//binaryNumber = "1010"
private static int iterative(String binaryNumber) {
	int power = 0;
	int decimal = 0;
	for (int index = 0; index < binaryNumber.length(); index++) {
		char chValue = binaryNumber.charAt(binaryNumber.length() - index - 1);
		int digit = Character.getNumericValue(chValue);
		decimal = decimal + digit * (int) Math.pow(2, power++);
	}
	return decimal;
} //output: decimal = 10

Method 3: Convert binary number to decimal in java (recursive method)

//binaryNumber = "1010"
private static int recursive(String binaryNumber) {
	int decimal = 0;
	int length = binaryNumber.length();
	if (length > 0) {
		String substring = binaryNumber.substring(1);
		int digit = Character.getNumericValue(binaryNumber.charAt(0));
		decimal = digit * (int) Math.pow(2, length - 1) + recursive(substring);
	}
	return decimal;
}//output: decimal = 10

The logical flow of recursive method for input binary string “1010” is shown in Fig 1.

Program: convert binary number to decimal (java, iterative & recursive)

package org.learn;

import java.util.Scanner;

public class BinaryToDecimal {

	public static void main(String[] args) {
		try (Scanner scanner = new Scanner(System.in)) {
			
			System.out.printf("1. Enter binary string : ");
			String binary = scanner.next();

			int decimal = toDecimalUsingParseInt(binary);
			System.out.printf("2. Binary to decimal - parseInt(%s,2) = %d ", binary, decimal);

			decimal = iterative(binary);
			System.out.printf("\n3. Binary to decimal - iterative(%s) = %d ", binary, decimal);

			decimal = recursive(binary);
			System.out.printf("\n4. Binary to decimal - recursive(%s) = %d ", binary, decimal);
		}
	}

	private static int toDecimalUsingParseInt(String binaryNumber) {
		return Integer.parseInt(binaryNumber, 2);
	}

	private static int iterative(String binaryNumber) {
		int power = 0;
		int decimal = 0;
		for (int index = 0; index < binaryNumber.length(); index++) {
			char chValue = binaryNumber.charAt(binaryNumber.length() - index - 1);
			int digit = Character.getNumericValue(chValue);
			decimal = decimal + digit * (int) Math.pow(2, power++);
		}
		return decimal;
	}

	private static int recursive(String binaryNumber) {
		int decimal = 0;
		int length = binaryNumber.length();
		if (length > 0) {
			String substring = binaryNumber.substring(1);
			int digit = Character.getNumericValue(binaryNumber.charAt(0));
			decimal = digit * (int) Math.pow(2, length - 1) + recursive(substring);
		}
		return decimal;
	}
}

Output: convert binary number to decimal (java, iterative & recursive)

1. Enter binary string : 1010
2. Binary to decimal - parseInt(1010,2) = 10 
3. Binary to decimal - iterative(1010) = 10 
4. Binary to decimal - recursive(1010) = 10 

1. Enter binary string : 11100110
2. Binary to decimal - parseInt(11100110,2) = 230 
3. Binary to decimal - iterative(11100110) = 230 
4. Binary to decimal - recursive(11100110) = 230