Java Program to Implement Booth Algorithm

This is a Java Program to implement Booth Algorithm. This is a program to compute product of two numbers by using Booth’s Algorithm. This program is implemented for multiplying numbers in the range -7 to 7. However same principle can be extended to other numbers too.

Here is the source code of the Java program to implement Booth Algorithm. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

/**
 ** Java Program to Implement Booth Algorithm
 **/
 
import java.util.Scanner;
 
/** Class Booth **/
public class Booth
{
    public static Scanner s = new Scanner(System.in);
    /** Function to multiply **/
    public int multiply(int n1, int n2)
    {
        int[] m = binary(n1);
        int[] m1 = binary(-n1);
        int[] r = binary(n2);        
        int[] A = new int[9];
        int[] S = new int[9];
        int[] P = new int[9];        
        for (int i = 0; i < 4; i++)
        {
            A[i] = m[i];
            S[i] = m1[i];
            P[i + 4] = r[i];
        }
        display(A, 'A');
        display(S, 'S');
        display(P, 'P');        
        System.out.println();
 
        for (int i = 0; i < 4; i++)
        {
            if (P[7] == 0 && P[8] == 0);
                // do nothing            
            else if (P[7] == 1 && P[8] == 0)
                add(P, S);                            
            else if (P[7] == 0 && P[8] == 1)
                add(P, A);            
            else if (P[7] == 1 && P[8] == 1);
                // do nothing
 
            rightShift(P);
            display(P, 'P');
        }
        return getDecimal(P);
    }
    /** Function to get Decimal equivalent of P **/
    public int getDecimal(int[] B)
    {
        int p = 0;
        int t = 1;
        for (int i = 7; i >= 0; i--, t *= 2)
            p += (B[i] * t);
        if (p > 64)
            p = -(256 - p);
        return p;        
    }
    /** Function to right shift array **/
    public void rightShift(int[] A)
    {        
        for (int i = 8; i >= 1; i--)
            A[i] = A[i - 1];        
    }
    /** Function to add two binary arrays **/
    public void add(int[] A, int[] B)
    {
        int carry = 0;
        for (int i = 8; i >= 0; i--)
        {
            int temp = A[i] + B[i] + carry;
            A[i] = temp % 2;
            carry = temp / 2;
        }        
    }
    /** Function to get binary of a number **/
    public int[] binary(int n)
    {
        int[] bin = new int[4];
        int ctr = 3;
        int num = n;
        /** for negative numbers 2 complment **/
        if (n < 0)
            num = 16 + n;
        while (num != 0)
        {
            bin[ctr--] = num % 2;
            num /= 2;
        }
        return bin;
    }
    /** Function to print array **/
    public void display(int[] P, char ch)
    { 
        System.out.print("\n"+ ch +" : ");
        for (int i = 0; i < P.length; i++)
        {
            if (i == 4)
                System.out.print(" ");
            if (i == 8)
                System.out.print(" ");
            System.out.print(P[i]);
        } 
    }
    /** Main function **/
    public static void main (String[] args) 
    {
        Scanner scan = new Scanner(System.in);
        System.out.println("Booth Algorithm Test\n");
        /** Make an object of Booth class **/
        Booth b = new Booth();
 
        /** Accept two integers **/
        System.out.println("Enter two integer numbers\n");
        int n1 = scan.nextInt();
        int n2 = scan.nextInt();
        int result = b.multiply(n1, n2);
        System.out.println("\n\nResult : "+ n1 +" * "+ n2 +" = "+ result);                    
    }
}

Booth Algorithm Test
 
Enter two integer numbers
 
7 -7
 
A : 0111 0000 0
S : 1001 0000 0
P : 0000 1001 0
 
P : 1100 1100 1
P : 0001 1110 0
P : 0000 1111 0
P : 1100 1111 1
 
Result : 7 * -7 = -49