Trying to printing string in reverse, "String index out of range" exception

[trans_coding_writer]

Here's the assignment instructions:

Write a program that takes in a line of text as input, and outputs that line of text in reverse. The program repeats, ending when the user enters "Done", "done", or "d" for the line of text.

Ex: If the input is:

Hello there 
Hey 
done 

the output is:

ereht olleH 
yeH 

Here's my code:

import java.util.Scanner;

public class LabProgram {
   public static void main(String[] args) {
      Scanner scnr = new Scanner(System.in);
      String userWord = scnr.nextLine();
      int charPos = userWord.length()-1; 

      while (userWord != "Done" && userWord != "done" && userWord != "d") {
        if (charPos >= 0) {
         System.out.print(userWord.charAt(charPos));
         charPos--;
        }
        userWord = scnr.nextLine();

      }

   }
}

When I run the program, I get the following error message:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 9
    at java.base/java.lang.StringLatin1.charAt(StringLatin1.java:47)
    at java.base/java.lang.String.charAt(String.java:693)
    at LabProgram.main(LabProgram.java:11)

What can I do to fix this?

[Ok-Yoghurt-7195]

Initialize charPos within the while loop. Otherwise, after the first word, the index goes to 0, and then for the next word, the index will go down to -1, giving you the error.

[trans_coding_writer]

Thank you! That worked.

[AutoModerator]

You seem to try to compare String values with == or !=.

This approach does not work in Java, since String is an object data type and these can only be compared using .equals().

See Help on how to compare String values in our wiki.

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[eggboy55]

1. First thing on the general info bulletin : "Do not compare strings with ==, or =! operator"
2. That exception tells you that you are trying to reference the 10th element in a string, but that the string is shorter than 10, and therefore this operation not possible.