Error

[Mon Sep 15 - 09:36:15] [elliottcable @ Geoffrey] [~/Code/school/]
-- javac Exercises.java && java Exercises
Exercises.java:11: cannot find symbol
symbol  : method getCharAt(int)
location: class java.lang.String
    char last_character = input.getCharAt(last_char_index);
                               ^
1 error
[Mon Sep 15 - 09:42:34] [elliottcable @ Geoffrey] [~/Code/school/]
-- 

Exercises.java

import java.util.Scanner;

public class Exercises {
  static Scanner keyboard = new Scanner(System.in);
  
  public static void main(String[] args) {
    System.out.println("Hello! Say something...");
    String input = keyboard.next();
    
    int last_char_index = input.length() - 1;
    char last_character = input.getCharAt(last_char_index);
    System.out.println();
  }
  
}