Question

Java

1. Asks the user to enter a binary number ,example: 1011011
2. Validates that the entry is a binary number. Nothing but a binary number should be allowed.
3. The program converts and displays the binary number to its base 10 equivalent, Example 111₂ = 7₁₀
4. The user must be asked if he/she wants to continue entering numbers or quit.
5. Keeps a record in a txt file named outDataFile.txt with the history of all numbers entered and the associated results, in the following format:

Sample Output

You entered 111 Its base 10 equivalent is 7

1. No infinite loops, examples include:
   1. for(;;)
   2. while(1)
   3. while(true)
   4. do{//code}while(1);
2. No break statements to exit loops
3. No labels or go-to statements
4. If you violate any of these restrictions, you will automatically get a score of ZERO!

SPECIFIC RESTRICTIONS FOR THIS ACTIVITY

You should develop your own method, do not use Integer.parseInt (String s, int radix)

*********************************************************************************************************************************

This is my code so far, it works but once I ask the user to try another binary. The Binary doesn't come out right

***********************

import java.util.Scanner; // Needed for the Scanner class
import java.io.*; // Needed for File I/O classes

public class Binary
{
public static void main(String[] args) throws IOException
{

   String userEntry; // To hold the userEntry
   String again = "y";
   int binary = 0;
   int bin = 0;
   int decimal = 0;
   int i = 0;

// Create a Scanner object to read input.
Scanner keyboard = new Scanner(System.in);

   PrintWriter outputFile = new PrintWriter("outDataFile.txt");

   while (again.equalsIgnoreCase("y"))
{

        // Get the user's name.
           System.out.println("Enter a Binary String: ");
           userEntry = keyboard.nextLine();
           System.out.println("\nYou entered the number: " + userEntry );
           outputFile.println("You entered the number: " + userEntry);

           //validate userName
           userEntry = checkUserEntry (userEntry);
           binary = Integer.parseInt(userEntry);
           boolean result = isBinary(binary);

           if(result == true)
      {
           bin = binary;

           while(binary != 0)
       {
           decimal += (binary%10)*Math.pow(2, i++);
           binary = binary /10;

       }
           System.out.println("its base 10 equivalent of " + bin +" is " + decimal );
           outputFile.println("its base 10 equivalent of " + bin +" is " + decimal );
       }
       else
       {
           System.out.println("This is not a Binary Number, try again");
       }

       System.out.println("\n\nWould you like to try another number? (y/Y). Anything else will quit");
       again = keyboard.nextLine();

      }
      outputFile.close();
      System.out.println("Goodbye");

}//end main

   public static boolean isBinary(int binary)
   {
       int Input = binary;
           while (Input != 0)
               {
                   if (Input % 10 > 1)
                   {
                       return false;
                   }
           Input = Input / 10;
               }
                       return true;
   }

public static String checkUserEntry (String userAnswer)
{

   int userAnswerLength = userAnswer.length();
   int counter = 0;//to iterate through the string
   // Create a Scanner object to read input.
Scanner keyboard = new Scanner(System.in);

   while(userAnswerLength==0)
   {
               System.out.println("That is not a number >= 0, try again");
               userAnswer = keyboard.nextLine();
               userAnswerLength = userAnswer.length();
       }

   while(counter < userAnswerLength)
   {
           if(!Character.isDigit(userAnswer.charAt(counter)))
           {
               System.out.println("That is not a number >= 0, try again ");
               userAnswer = keyboard.nextLine();
               userAnswerLength = userAnswer.length();
               counter = 0;
           }
           else
           {
               counter++;
           }
           while(userAnswerLength==0)
           {
                  System.out.println("That is not a number >= 0, try again");
                   userAnswer = keyboard.nextLine();
                   userAnswerLength = userAnswer.length();
           }
       }

       return userAnswer;
}

}//end class ValidateUserName

Answer 1

SOLUTION:

There were 2 problems in the following code:

if(result == true)
{
bin = binary;

while(binary != 0)
{
decimal += (binary%10)*Math.pow(2, i++);
binary = binary /10;

}

decimal variable should be reset to 0 before starting next binary number. Similarly i should be reset to 0 before starting conversion.

With fix code will be:

if(result == true)
{
bin = binary;
decimal = 0;
i = 0;

while(binary != 0)
{
decimal += (binary%10)*Math.pow(2, i++);
binary = binary /10;

}

Other thing I noticed there is a note given for not to use parseInt method, but your code still uses it.

To avoid parseInt method use, changed the code to use String input only.

Solution is to parse the string character by character and to convert character to its equivalent integer value subtract '0' from character. The result will be the digit.

Changed the isBinary() method to use String input only to validate if the number entered is valid binary input or not.

CODE:

import java.util.Scanner; // Needed for the Scanner class
import java.io.*; // Needed for File I/O classes

public class Binary
{
public static void main(String[] args) throws IOException
{
String userEntry; // To hold the userEntry
String again = "y";
int binary = 0;
int bin = 0;
int decimal = 0;
int i = 0;

// Create a Scanner object to read input.
Scanner keyboard = new Scanner(System.in);

PrintWriter outputFile = new PrintWriter("outDataFile.txt");

while (again.equalsIgnoreCase("y"))
{
// Get the user's name.
System.out.println("Enter a Binary String: ");
userEntry = keyboard.nextLine();
System.out.println("\nYou entered the number: " + userEntry );
outputFile.println("You entered the number: " + userEntry);

//validate userName
userEntry = checkUserEntry (userEntry);
boolean result = isBinary(userEntry); // pass the string only
  
int length = userEntry.length();
int index = 0;

if(result == true)
{
bin = binary;
decimal = 0; //reset decimal
i = 0; // reset i to 0
index = length - 1;

while(length-- != 0) // loop till length becomes 0
{
decimal += ((userEntry.charAt(index--) - '0') % 10) * Math.pow(2, i++); // subtract '0' to get integer value

}
System.out.println("its base 10 equivalent of " + userEntry +" is " + decimal );
outputFile.println("its base 10 equivalent of " + userEntry +" is " + decimal );
}
else
{
System.out.println("This is not a Binary Number, try again");
}

System.out.println("\n\nWould you like to try another number? (y/Y). Anything else will quit");
again = keyboard.nextLine();
}
outputFile.close();
System.out.println("Goodbye");
}//end main

public static boolean isBinary(String binary)
{
int length = binary.length();
int index = length - 1;
while (length-- != 0) // loop till length becomes 0
{
if ((binary.charAt(index--) - '0') % 10 > 1) // extract character and subtract '0' to get integer value
{
return false;
}
}
return true;
}

public static String checkUserEntry (String userAnswer)
{

int userAnswerLength = userAnswer.length();
int counter = 0;//to iterate through the string
// Create a Scanner object to read input.
Scanner keyboard = new Scanner(System.in);

while(userAnswerLength==0)
{
System.out.println("That is not a number >= 0, try again");
userAnswer = keyboard.nextLine();
userAnswerLength = userAnswer.length();
}

while(counter < userAnswerLength)
{
if(!Character.isDigit(userAnswer.charAt(counter)))
{
System.out.println("That is not a number >= 0, try again ");
userAnswer = keyboard.nextLine();
userAnswerLength = userAnswer.length();
counter = 0;
}
else
{
counter++;
}
while(userAnswerLength==0)
{
System.out.println("That is not a number >= 0, try again");
userAnswer = keyboard.nextLine();
userAnswerLength = userAnswer.length();
}
}

return userAnswer;
}
}//end class ValidateUserName

OUTPUT:

outDataFile.txt