Java Program to Convert Binary to Decimal

Introduction

Converting a binary number to its decimal equivalent is a fundamental task in computing. Binary numbers are base-2 numbers, consisting only of 0s and 1s, while decimal numbers are base-10 numbers, which are commonly used in everyday arithmetic. This guide will walk you through writing a Java program that converts a given binary number to its decimal equivalent.

Problem Statement

Create a Java program that:

• Prompts the user to enter a binary number.
• Converts the binary number to its decimal equivalent.
• Displays the decimal equivalent.

Example:

• Input: "1010"

• Output: "Decimal of 1010 is 10"

• Input: "1111"

• Output: "Decimal of 1111 is 15"

Solution Steps

1. Read the Binary Number: Use the Scanner class to take the binary number as input from the user.
2. Convert Binary to Decimal: Use either the built-in method Integer.parseInt() or manually convert the binary number using a loop.
3. Display the Result: Print the decimal equivalent.

Java Program Using Built-in Method

// Java Program to Convert Binary to Decimal using Integer.parseInt() // Author: https://www.rameshfadatare.com/ import java.util.Scanner; public class BinaryToDecimal { public static void main(String[] args) { // Step 1: Read the binary number from the user try (Scanner scanner = new Scanner(System.in)) { System.out.print("Enter a binary number: "); String binary = scanner.nextLine(); // Step 2: Convert the binary number to decimal using built-in method int decimal = Integer.parseInt(binary, 2); // Step 3: Display the result System.out.println("Decimal of " + binary + " is " + decimal); } } } 

Java Program Using a Manual Conversion Method

// Java Program to Convert Binary to Decimal without using Integer.parseInt() // Author: https://www.rameshfadatare.com/ import java.util.Scanner; public class BinaryToDecimalManual { public static void main(String[] args) { // Step 1: Read the binary number from the user try (Scanner scanner = new Scanner(System.in)) { System.out.print("Enter a binary number: "); String binary = scanner.nextLine(); // Step 2: Convert the binary number to decimal manually int decimal = 0; int power = 0; for (int i = binary.length() - 1; i >= 0; i--) { int digit = binary.charAt(i) - '0'; // Convert char to int decimal += digit * Math.pow(2, power); power++; } // Step 3: Display the result System.out.println("Decimal of " + binary + " is " + decimal); } } } 

Explanation

Step 1: Read the Binary Number

• The Scanner class is used to read a binary number input from the user as a string. The nextLine() method captures the input.

Step 2: Convert Binary to Decimal

• Using Built-in Method:
  • The Integer.parseInt(binary, 2) method converts a binary string directly to its decimal equivalent. The second argument, 2, specifies the base of the input number.
• Manual Conversion:
  • The program iterates through each digit of the binary number string, starting from the least significant bit (rightmost digit).
  • For each digit, it multiplies the digit by 2 raised to the power of its position (starting from 0) and adds the result to the cumulative decimal value.

Step 3: Display the Result

• The program prints the decimal equivalent of the binary number using System.out.println().

Output Example

Example 1: Using Built-in Method

Enter a binary number: 1010 Decimal of 1010 is 10 

Example 2: Using Manual Conversion

Enter a binary number: 1111 Decimal of 1111 is 15 

Example 3: Handling a Larger Binary Number

Enter a binary number: 100110 Decimal of 100110 is 38 

Conclusion

These Java programs demonstrate how to convert a binary number to its decimal equivalent using both a built-in method and a manual conversion process. The solutions provided cover basic concepts such as loops, arithmetic operations, and string manipulation, making them valuable exercises for beginners learning Java programming.