Doesn't pass the verification

Question about the task

Under discussion

Can somebody tell my why this code doesn't pass? I know the values aren't right but I followed the algorithm and I don't understand where is the mistake.

The public static toOctal(int) method must convert the integer received as an input parameter from the decimal numeral system into octal. And conversely, the public static toDecimal(int) method converts from the octal system into decimal.
The methods only work with positive numbers. If the input parameter is less than or equal to 0, the methods return 0.
Your task is to implement these methods.

One algorithm for converting a decimal number to octal is as follows:


i is equal to 0
while (the decimal number is not 0) {
the octal number = the octal number + (remainder of the division of the decimal number by 8) * 10 to the power of i
the decimal number = the decimal number / 8
increase i by 1
}

One algorithm for converting an octal number to decimal is as follows:


i is equal to 0
while (the octal number is not 0) {
the decimal number = the decimal number + (remainder of the division of the octal number by 10) * 8 to the power of i
the octal number = the octal number / 10
increase i by 1
}

The main() method is not involved in testing.

Hint: You can use the Math.pow(number, degree) method to raise a number to a power.

Requirements:

The toOctal(int) method needs to be implemented as outlined in the task conditions.
The toDecimal(int) method needs to be implemented as outlined in the task conditions.
The Integer.toOctalString(int) and Long.toOctalString(int) methods cannot be used.
The Integer.parseInt(String, int) and Long.parseLong(String, int) methods cannot be used.
The Integer.toString(int, int) and Long.toString(long, int) methods cannot be used.
You cannot use a BigInteger object.
You cannot use a BigDecimal object.

package en.codegym.task.pro.task09.task0905; /* Octal converter */ public class Solution { public static void main(String[] args) { int decimalNumber = 21; // System.out.println((decimalNumber % 8) * 10); System.out.println("Decimal number " + decimalNumber + " is equal to octal number " + toOctal(decimalNumber)); int octalNumber = 25; // System.out.println((octalNumber % 10) * 8); System.out.println("Octal number " + octalNumber + " is equal to decimal number " + toDecimal(octalNumber)); } public static int toOctal(int decimalNumber) { int i = 0; int octalNumber = 0; int divisionRemainder = (decimalNumber % 8) * 10; if (decimalNumber > 0) { while (decimalNumber != 0) { octalNumber = (int) (octalNumber + Math.pow(divisionRemainder, i)); decimalNumber = decimalNumber / 8; i++; } return (int) octalNumber; } return 0; } public static int toDecimal(int octalNumber) { int i = 0; int decimalNumber = 0; int divisionRemainder = (octalNumber % 10) * 8; if (octalNumber > 0) { while (octalNumber != 0) { decimalNumber = (int) (decimalNumber + Math.pow(divisionRemainder, i)); octalNumber = octalNumber / 10; i++; } return (int) decimalNumber; } return 0; } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

9 May 2023, 13:29

Your octal algorithm doesn't do what the task says. Your code with notes:

public static int toOctal(int decimalNumber) {
   int i = 0;  // i is equal to 0 (complete)
   int octalNumber = 0;

   /* ↓ don't know what this line is, it doesn't say to do this anywhere
    the division remainder should be calculated in the loop
    and multiplied by 10 to the power of i each cycle */
   int divisionRemainder = (decimalNumber % 8) * 10;

   if (decimalNumber > 0) {
      while (decimalNumber != 0) {  // while (the decimal number is not 0)  (complete)

         /* this line should be the octalNum = octalNum  + (remainder of the division
         of the decimal number by 8) * 10 to the power of i */
         octalNumber = (int) (octalNumber + Math.pow(divisionRemainder, i));
         /* the line of code you wrote above doesn't do this. It instead does:
         octalNum = OctalNum + divisionRemainder to the power of i
         re-read the instructions and implement properly*/

         //the decimal number = the decimal number / 8  (complete)
         decimalNumber = decimalNumber / 8;

         // increase i by 1 (complete)
         i++;
      }

      // octalNumber is already an int, no need to cast here (int)
      return (int) octalNumber;
   }
   return 0;
}

I didn't check the toDecimal method but once you fix the toOctal method you should be able to fix that one as well..