Thread: Need some help with my code

Hey if someone could help me shed some light on my code as too why it is getting the error String index out of range: -1 i would be for ever in your debt

the part of the question im stuck on is this
"At the beginning, your program should ask the user to specify a one-to-one mapping between the
characters in the above mentioned alphabet. For example, your program may display the 40 characters
in one line and ask the user to type the same set of characters in the second line, but in a different
order. After the mapping is established, your program should then ask the user to type in a sentence
using the characters from this alphabet, and then output the encrypted sentence"

The bit in red is the bit im really stuck on

Code:

package question3;

import java.util.Scanner;

public class Question3 {
private String alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890 ,.!";
private String MAP = "";
private String Pass = "";
Scanner kb = new Scanner(System.in);

public void getString(){

System.out.println("These are the Characters that are able to be used");
System.out.println(alpha);
System.out.println("Please input encryption");
MAP = kb.nextLine();
MAP = MAP.toUpperCase();
}

public void checkalpha(){
int firstIndex = 0;
int lastIndex = 0;
int count = 1;

boolean repeatedChars = false;

if(MAP.length() == 40){

for (int i = 0; count < MAP.length(); i++){

char character = MAP.charAt(i);
firstIndex = MAP.indexOf(character);
lastIndex = MAP.lastIndexOf(character);


if(firstIndex != lastIndex) {
repeatedChars = true;
}
count++;
}

if(repeatedChars == true) {
System.out.println("There were repeated characters in the string");
System.out.println("Please Do not Input the characters more than Once");
}
else {
System.out.println("No Repeated Characters");
}
if (MAP.equals(alpha)){
System.out.println("Please Do not repeat the starting characters");
getString();

}
}
else {
System.out.println("Incorrect Amount of Characters");
System.out.println("");
}

}

public void printConverted(){

char PassIndex;

System.out.println("Please Input message wanted to be converted");
Pass = kb.nextLine();
for (int i = 0; i < Pass.length(); i++){

PassIndex = MAP.charAt(Pass.indexOf(alpha.charAt(i)));
System.out.println(PassIndex);
}

}

printConverted method is the one with the problem, im positive about that.

Thanks for taking a look, if you need more info about something please let me know, i am very new to java so i really want to learn what im doing wrong

Please Edit your post and wrap your code with
[code=java]
<YOUR CODE HERE>
[/code]
to get highlighting and preserve formatting.

You should post the full text of the error message that shows where the error happens.

why it is getting the error

Because the index being used has an invalid value. You should check that the variable has a valid value before using it to index a String. It looks like you are assuming the value a method returns is valid. The method can return a -1 that you need to test for BEFORE using it.