stuck on java program converting user input string representing binary number to decimal

user_18273596 0
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Java Program. Eclipse IDE most recent. java 17.0.1.

program should prompt user a string representing a binary number. word must be 8 digits or less and must contain only 1s and 0s. If word is not 8 digits or less program should prompt user to make it such. If input does not contain only 1s and 0s, program should prompt user to only include 1s and 0s. I will post code that i have so far, i know that it is incomplete but im pretty much frozen where im at not sure where to go with it.

        public static void main(String[] args) {
            boolean isValid=false;
            String bin = "";
            int power =0;
            int x=0;
            long decimal = 0;
            int answer=0;
            Scanner sc = new Scanner(System.in);//create input method
            do {        
                System.out.println("Please enter a binary number: ");//prompt user for binary number
                bin = sc.nextLine();//bin equals input 
                if(bin.length()<=8) {//if length is 8 or less digits
                    for(int i =bin.length()-1; i>=0; i--) {//for the char at index i
                        if(((bin.charAt(i)=='1'))||(bin.charAt(i)=='0')){
                            isValid=true;   
                            x=bin.indexOf(i);
                            power++;//power increase by 1 for each digit 
                            decimal=(long)Math.pow(2,power);
        
                            System.out.println("The binary number you entered converted to decimal is: " + decimal);
                            break;
                        }else
                            isValid=false;
                            System.out.println("Invalid number. Please enter binary number containing only 1s and 0s:");
                    }
                }else 
                    System.out.println("Invalid number. Please enter binary number with 8 or less digits: ");
            }
            while(isValid=true);
        }
    }

output i get is:

Please enter a binary number: 
0101
The binary number you entered converted to decimal is: 1
Please enter a binary number: 
1111
The binary number you entered converted to decimal is: 2
Please enter a binary number: 
1111111
The binary number you entered converted to decimal is: 4
Please enter a binary number: 
111
The binary number you entered converted to decimal is: 8
Please enter a binary number: 
11
The binary number you entered converted to decimal is: 16
Please enter a binary number: 
01
The binary number you entered converted to decimal is: 32
Please enter a binary number:
decimal binary java
1 Answers

I fixed the code for you.

  • The result of Math.pow() is added to decimal when the digit is one, and moved this line before power++ because if the last digit is 1 it would have a value of 1 but the original code would add 2. 2 to the power of 0 is 1, so not incrementing power before the first pow is correct.
  • Moved break to the else condition and moved the output of the decimal number to be the last line of the loop.
  • Added missing curly brackets to both of the else clauses. With break removed, the Invalid number is always printed.
  • Initialize decimal and power to zero at beginning of loop. Without setting these to zero, subsequent numbers converted give the wrong output.
  • Only prints the result if it is valid.
  • Go to next iteration with continue if number is more than 8 digits.
        public static void main(String[] args) {
            boolean isValid=false;
            String bin = "";
            int power =0;
            int x=0;
            long decimal = 0;
            int answer=0;
            Scanner sc = new Scanner(System.in);//create input method
            do {        
                System.out.println("Please enter a binary number: ");//prompt user for binary number
                decimal = 0;
                power = 0;
                bin = sc.nextLine();//bin equals input 
                if(bin.length()<=8) {//if length is 8 or less digits
                    for(int i =bin.length()-1; i>=0; i--) {//for the char at index i
                        if(((bin.charAt(i)=='1'))||(bin.charAt(i)=='0')){
                            isValid=true;   
                            x=bin.indexOf(i);
                            if(bin.charAt(i) == '1'){
                                decimal+=(long)Math.pow(2,power);
                            }
                            power++;//power increase by 1 for each digit 
        
                        }else {
                            isValid=false;
                            System.out.println("Invalid number. Please enter binary number containing only 1s and 0s:");
                            break;
                        }
                    }
                }else {
                    System.out.println("Invalid number. Please enter binary number with 8 or less digits: ");
                    continue;
                }
                if (isValid) {
                    System.out.println("The binary number you entered converted to decimal is: " + decimal);
                }
            }
            while(isValid=true);
        }

Output:

Please enter a binary number:
11000110
The binary number you entered converted to decimal is: 198 
Please enter a binary number:
10100010
The binary number you entered converted to decimal is: 162
88437640
Invalid number. Please enter binary number containing only 1s and 0s:
Please enter a binary number:
123456789
Invalid number. Please enter binary number with 8 or less digits:
Please enter a binary number:
11111111                                                                                                                The binary number you entered converted to decimal is: 255                                                              Please enter a binary number:  
^C
user_88903450
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