octal to decimal conversion Java

import java.util.Scanner;

public class OctalConversion {

// simple main method for static Java little job

public static void main(String[] arg) {

// Scanner to read user input

Scanner scan = new Scanner(System.in);

// prompt for String

System.out.print("Enter octal number: ");

// read it back

String octalStr = scan.nextLine();

// convert to int

int dec = convertToDecimal(octalStr);

// if not -1 conversion was OK

if(dec != -1)

System.out.println("Octal: " + octalStr + " is in decimal " + dec);

}

static int convertToDecimal(String octo) {

int number = 0;      // init result

for(int i = 0; i < octo.length(); i++) { // pass through all input characters

char digit = octo.charAt(i);            // fetch octal digit

digit -= '0';                           // translate to number (integer)

if(digit < 0 || digit > 7) {          // validate user inpu

System.out.println("Your number is NOT a valid Octal number");

return -1;

}

number *= 8;                            // shift to left what I already ahve

number += digit;                        // add new number

}

return number;

}

}