Write a function that takes a string as input and returns the string reversed.

Example:

Given s = "hello", return "olleh".

public class Solution {
    public String reverseString(String s) {
        StringBuilder sb = new StringBuilder();
        for(int i=s.length()-1;i>=0;i--){
        	sb.append(s.charAt(i));
        }
        return sb.toString();
    }
}