Java add leading zeros to a number

Question

I need to return a string in the form xxx-xxxx where xxx is a number and xxxx is another number, however when i have leading zeros they disappear. I'm trying number formatter, but it's not working.

 public String toString(){
        NumberFormat nf3 = new DecimalFormat("#000");
        NumberFormat nf4 = new DecimalFormat("#0000");
        if( areaCode != 0)
            return nf3.format(areaCode) + "-" + nf3.format(exchangeCode) + "-" + nf4.format(number);
        else
            return exchangeCode + "-" + number;
    }

}

I figured it out:

 public String toString(){
        NumberFormat nf3 = new DecimalFormat("000");
        NumberFormat nf4 = new DecimalFormat("0000");
        if( areaCode != 0)
            //myFormat.format(new Integer(someValue));
            return nf3.format(new Integer(areaCode)) + "-" + nf3.format(new Integer(exchangeCode)) + "-" + nf4.format(new Integer(number));
        else
            return nf3.format(new Integer(exchangeCode)) + "-" + nf4.format(new Integer(number));
    }

Answer 1

When areaCode is 0, you forget to call format! Other than that, it looks fine. The leading "#" are not necessary, but won't cause any problems for valid inputs.

I just tried it out real quick to check and it worked fine for me.

public static String formatTest(int areaCode, int exchangeCode, int number) {
    DecimalFormat nf3 = new DecimalFormat("#000");
    DecimalFormat nf4 = new DecimalFormat("#0000");
    if( areaCode != 0)
        return nf3.format(areaCode) + "-" + nf3.format(exchangeCode) + "-" + nf4.format(number);
    else
        return nf3.format(exchangeCode) + "-" + nf4.format(number);
}


public static void main(String[] args) {
    System.out.println(formatTest(12, 90, 8));
    System.out.println(formatTest(1, 953, 1932));
}

Output:

012-090-0008
001-953-1932