Bin2Dec.java

import java.util.Scanner; // for user input

public class Bin2Dec {

    /**
    *   Program:    Bin2Dec.java
    *   Purpose:    Convert binary number to decimal
    *   Creator:    Chris Clarke
    *   Created:    21.09.2009
    *   Modified:   25.03.2013 (Scanner)
    */

    public static int convertBin2Dec(String s) {
        int sum = 0;
        int multiplier = 0;
        for (int i = s.length()-1; i>=0; i--) { // work from right to left (1, 2, 4, 8 etc)
            if (s.charAt(i) == '1') {
                sum += Math.pow(2, multiplier); // add (2 ^ multiplier) to sum
            }//end if
            multiplier++; // increment multiplier
        }//end for
        return sum;
    }//end convertBin2Dec

    public static void main(String[] args) {
        if (args.length==1) { // user typed binary number as argument
            // method call outputs decimal number
            System.out.println( convertBin2Dec( args[0]));
            System.exit(0); // exit program
        }//end if

        Scanner scan = new Scanner(System.in); // create scanner object
        System.out.print("Enter binary number: "); // prompt
        String bin = scan.nextLine(); // get input from user
        System.out.println( convertBin2Dec( bin)); // method call outputs decimal number
    }//end main
}//end class