The problem belongs to LeetCode, here is the link to the problem

Following code segment contains the description in the class comments, followed by fully working solution

/**
 * Write a function that reverses a string. The input string is given as an array of characters s.
 *
 * You must do this by modifying the input array in-place with O(1) extra memory.
 *
 * Example 1:
 *
 * Input: s = ["h","e","l","l","o"]
 * Output: ["o","l","l","e","h"]
 */
public class ReverseString {
    public void reverseString(char[] s) {
		// method;
        for(int i=0; i < s.length/2; i++){
            char t=s[i];
            s[i]=s[s.length-i-1];
            s[s.length-i-1]=t;
        }
    }
}