Write a function to convert an IPv4 Address in string format to an unsigned integer

import java.lang.*;
public class IPtoNum
{
public static double IPAddressToNumber(String IPaddress1)
{
int i;
String [] arrDec=null;
double num = 0;
if (IPaddress1 == "")
{
return 0;
}
else
{
String delimiter = "\\.";
arrDec = IPaddress1.split(delimiter);
System.out.println(arrDec.length);
for(i = arrDec.length - 1; i >= 0 ; i --)
{
num += ((Integer.parseInt(arrDec[i])%256) * Math.pow(256 ,(3 - i )));
}
return num;
}
}
public static void main(String args[])
{
System.out.println(IPAddressToNumber(args[0]));
}
}