Converting form Decimal to Binary in Java

Problem:

Write a program that reads a string in binary form from the user (i.e of the form "001010101") and returns the integer equivalent of the string (starting from right to left for the lest significant bit). For example, "0101" is from right to left:

(1* 2^0) + (0* 2^1) + (1* 2^2) + (2* 2^3) which is equal to 5.

Output:

Please enter the binary string:
0001 
The integer value is 1

Solution:

There are two methods to solve this problem. They are listed respectively.

import java.util.Scanner;
public class Problem2version1 
{
 
 public static void main(String[] args)
 {
  Scanner scan=new Scanner(System.in);
  
  System.out.println("Please enter the binary string:");
  String input=scan.next();
  int sum=0;
  int power2=1;
  for(int n=input.length()-1;n>=0;n--)
  {
   if(input.charAt(n)=='1')
    sum += power2;
    
   power2 *= 2;
  }
  System.out.println("The integer value is "+sum);
 }
}

import java.util.Scanner;

public class Problem2
{
 public static void main(String [] args)
 {
  Scanner scan = new Scanner(System.in);
  System.out.println("Please enter the binary string: ");
  String s = scan.next();
  int L = s.length();
  int i = 0;//iterator
      double k = 0;//the value of 1 in the string everytime
  double sum = 0;//the total sum
 
  while (i