Java: Multiply two binary numbers

Java Basic: Exercise-18 with Solution

Write a Java program to multiply two binary numbers.

In digital electronics and mathematics, a binary number is a number expressed in the base-2 numeral system or binary numeral system. This system uses only two symbols: typically 1 (one) and 0 (zero).

Test Data:
Input first binary number: 110
Input second binary number: 101

Sample Solution:

Java Code:

import java.util.Scanner;
public class Exercise18 {
 public static void main(String[] args) {
  // Declare variables to store two binary numbers and the product
  long binary1, binary2, multiply = 0;
  
  // Initialize digit and factor variables for processing binary2
  int digit, factor = 1;
  
  // Create a Scanner object to read input from the user
  Scanner in = new Scanner(System.in);
  
  // Prompt the user to input the first binary number
  System.out.print("Input the first binary number: ");
  binary1 = in.nextLong();
  
  // Prompt the user to input the second binary number
  System.out.print("Input the second binary number: ");
  binary2 = in.nextLong();
  
  // Process binary2 to calculate the product
  while (binary2 != 0) {
   digit = (int)(binary2 % 10);
   if (digit == 1) {
    binary1 = binary1 * factor;
    multiply = binaryproduct((int) binary1, (int) multiply);
   } else {
    binary1 = binary1 * factor;
   }
   binary2 = binary2 / 10;
   factor = 10;
  }
  
  // Display the product of the two binary numbers
  System.out.print("Product of two binary numbers: " + multiply + "\n");
 }

 // Method to calculate the product of two binary numbers
 static int binaryproduct(int binary1, int binary2) {
  int i = 0, remainder = 0;
  int[] sum = new int[20];
  int binary_prod_result = 0;

  while (binary1 != 0 || binary2 != 0) {
   sum[i++] = (binary1 % 10 + binary2 % 10 + remainder) % 2;
   remainder = (binary1 % 10 + binary2 % 10 + remainder) / 2;
   binary1 = binary1 / 10;
   binary2 = binary2 / 10;
  }

  if (remainder != 0) {
   sum[i++] = remainder;
  }
  
  --i;
  
  while (i >= 0) {
   binary_prod_result = binary_prod_result * 10 + sum[i--];
  }

  return binary_prod_result;
 }
}
 

Explanation:

In the exercise above -

• Initialize variables to store the two binary numbers ('binary1' and 'binary2'), the result 'multiply', and other necessary variables.
• Take two binary numbers from the user using the Scanner class.
• Next, it enters a loop to perform binary multiplication by considering the digits of the second binary number one by one from right to left.
• For each digit in 'binary2', if it's 1, it multiplies 'binary1' by a factor. It computes the product using the "binaryproduct()" function.
• The helper function "binaryproduct()" calculates the binary product of two numbers and returns the result.
• If the digit in binary2 is 0, it still multiplies 'binary1' by the factor but doesn't perform the product calculation.
• It updates 'binary2' by moving to the next digit (right to left) and adjusting the factor.
• After the loop, it prints the product of the two binary numbers, which is stored in the multiply variable.

Sample Output:

Input the first binary number: 110                                                                            
Input the second binary number: 101                                                                           
Product of two binary numbers: 11110 

Flowchart:

Flowchart : binaryproduct()

Java Code Editor:

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