AtoF - Float Point Conversion

http://www.careercup.com/question?id=4901629824335872
Write atof in Java, which converts a string representation of a float (like "342.18E-10") to an actual float without using any built-in parsing functions.
https://github.com/mission-peace/interview/blob/master/src/com/interview/misc/FloatPointConversion.java
    public double convert(String input){
        boolean isNeg = false;
        if(input.startsWith("-")){
            isNeg = true;
            input = input.substring(1);
        }
        StringTokenizer strtk = new StringTokenizer(input,"E");
        String number = strtk.nextToken();
        String power = strtk.nextToken();
        double dNumber = toDouble(number);
        double dPower = toDouble(power);
        double pow = Math.pow(10, dPower);
        double result = dNumber * pow;
        return isNeg ? result * -1 : result;
    }
   
    private double toDouble(String number){
        boolean isNeg = false;
        if(number.startsWith("-")){
            isNeg = true;
            number = number.substring(1);
        }
        int result = 0;
        int pow = 1;
        boolean foundDot = false;
        for(char ch : number.toCharArray()){
            if(ch == '.'){
                foundDot = true;
                continue;
            }
            if(foundDot){
                pow = pow*10;
            }
            result *= 10;
            result += (ch - '0');
        }
       
        double doubleResult = (result*1.0)/pow;
       
        return isNeg ? doubleResult*-1 : doubleResult;
    }