getting java.lang.StringIndexOutOfBoundsException error
<p>while i am doing a simple cipher program. i was encounter this error</p>

<pre><code>Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1
at java.lang.String.charAt(Unknown Source)
at Caesar.main(Caesar.java:27)
</code></pre>

<p>well, i am not quite clear on what is the cause. i require some help from some veteran here @@ below are my code.</p>

<pre><code>import java.util.Scanner;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;

public class Caesar {

    public static void main(String[] args){
         String from = "abcdefghijklmnopqrstuvwxyz";
         String to   = "feathrzyxwvusqponmlkjigdcb";
            Scanner console = new Scanner(System.in);
            System.out.print("Input file: ");
            String inputFileName = console.next();
            System.out.print("Output file: ");
        String outputFileName = console.next();

        try{ 
            FileReader reader = new FileReader("C:/"+inputFileName+".txt");
            Scanner in = new Scanner(reader);
            PrintWriter out = new PrintWriter("C:/"+outputFileName+".txt");

                while (in.hasNextLine()){
                    String line = in.nextLine();
                    String outPutText = "";
                    for (int i = 0; i &lt; line.length(); i++){
                        char c = to.charAt(from.indexOf(line.charAt(i)));
                        outPutText += c;
                    }
                    System.out.println("Plaintext: " + line);
                    System.out.println("Ciphertext: " + outPutText);
                    out.println(outPutText);         
                }
                System.out.println("Processing file complete");
                out.close();
        }
        catch (IOException exception){ 
            System.out.println("Error processing file:" + exception);
        }
}
}
</code></pre>
