Question

JAVA:

Write a program that converts a binary number to decimal (integer)

Based on user input: Ask user to input a binary number

Conditions:

Check that the binary number starts with a 1 and only has 0s and 1s

If condition is not met, ask for user to reenter a number

Conver the binary to decimal (integer)

Ask user if they want to input another number if not then the program will exit

*Please do not use built-in java functions when converting binary to decimal

Answer 1

Please go through screenshots for reference .And check line numbers according to line numbers in screenshot you can easily understand.Have any doubts comment below.Thank you.

JAVA CODE:

import java.util.*;
public class BinaryToDecimal {
   public static void main(String args[])
   {
       System.out.print("Enter Binary number:");
       BinaryToDecimal.TakeInput();  
   }
   public static void TakeInput() //Method to Take input from user
   {
       Scanner sc = new Scanner(System.in);
       String number = sc.next(); //Taking input from user
      
       if(number.charAt(0)=='1') // Condition to check number starts with 1 or not
       {
           int n = Integer.parseInt(number);
           int l = 0;
           while(n>0)       // Loop to check number having only 0's or 1's
           {
               if(n%10==0 || n%10==1)
                   l++;
               n=n/10;
           }
           if(l==number.length()) // if it is binary number pass the number to convert to decimal
           {
               BinaryToDecimal.ToDecimal(Integer.parseInt(number));
           }
           else // number is not binary ask user to reenter the number
           {
               System.out.print("reenter a number:");
               BinaryToDecimal.TakeInput();  
           }
       }
       else // if number is not start with 1 ask user to reenter the number
       {
           System.out.println("reenter a number:");
           BinaryToDecimal.TakeInput();  
       }
   }
   public static void ToDecimal(int num) // method to change the binary number to decimal
   {
       int decimal=0,p=0;
       while(num>0)
       {
           decimal += (num%10)*Math.pow(2,p);
           num = num/10;
           p++;
       }
       System.out.println(decimal);
       System.out.print("If you want to input another number(y/n):"); // Ask user if you to enter another number
       Scanner sc1 = new Scanner(System.in);
       char ch = sc1.next().charAt(0);   // scaning character to y-for YES and n-for NO
      
       if(ch=='n') // if n (NO) EXIT form program
       {
           System.exit(0);
       }
       else // if y (YES) ask user to enter number
       {
           System.out.print("Enter the Binary number:");
           BinaryToDecimal.TakeInput();
       }      
   }
}