LeetCode Reverse Bits

Description:

Reverse bits of a given 32 bits unsigned integer.

For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as00111001011110000010100101000000).
Solution:

import java.util.*;

public class Solution {
public int reverseBits(int n) {
String s = Integer.toBinaryString(n);
n = 0;
int token = 1;

for (int i = 0; i < s.length(); i++) {
n = n | (s.charAt(i) - '0') * token;
token <<= 1;
}
for (int i = s.length(); i < 32; i++) {
n <<= 1;
}
return n;
}
}