Why does it give me this error and how can I fix it?


Exception in thread “main” java.lang.ArrayIndexOutOfBoundsException:0
             at Alphabet.main(Alphabet.jaba:9)


import java.io.*;
import java.util.*;

public class Alphabet
{
    public static void main(String args[] )
        throws IOException
    {
        BufferedReader in =
            new BufferedReader(
               new FileReader(args[0]));
        String delims =
            "How to program java";
        int totA = 0, totB = 0, totC = 0, totD = 0, totE = 0, totF = 0,
            totG = 0, totH = 0, totI = 0, totJ = 0, totK = 0, totL = 0,
            totM = 0, totN = 0, totO = 0,totP = 0, totQ = 0, totR = 0,
            totS = 0, totT = 0, totU = 0,totV = 0, totW = 0, totX = 0,
            totY = 0, totZ = 0;

        // Read lines:
        String line;
        while ((line = in.readLine()) != null)
        {
            // Tokenize line:
            StringTokenizer strtok =
                new StringTokenizer(line, delims, true);
            while (strtok.hasMoreTokens())
            {
                char vowel = strtok.nextToken().charAt(0);
                switch(Character.toLowerCase(vowel))
                {
                case 'a':
                    ++totA;
                    break;
                case 'b':
                    ++totB;
                    break;
                case 'c':
                    ++totC;
                    break;
                case 'd':
                    ++totD;
                    break;
                case 'e':
                    ++totE;
                    break;
                case 'f':
                    ++totF;
                    break;
                case 'g':
                    ++totG;
                    break;
                case 'h':
                    ++totH;
                    break;
                case 'i':
                    ++totI;
                    break;
                case 'j':
                    ++totJ;
                    break;
                case 'k':
                    ++totK;
                    break;
                case 'l':
                    ++totL;
                    break;
                case 'm':
                    ++totM;
                    break;
                case 'n':
                    ++totN;
                    break;
                case 'o':
                    ++totO;
                    break;
                case 'p':
                    ++totP;
                    break;
                case 'q':
                    ++totQ;
                    break;
                case 'r':
                    ++totR;
                    break;
                case 's':
                    ++totS;
                    break;
                case 't':
                    ++totT;
                    break;
                case 'u':
                    ++totU;
                    break;
                case 'v':
                    ++totV;
                    break;
                case 'w':
                    ++totW;
                    break;
                case 'x':
                    ++totX;
                    break;
                case 'y':
                    ++totY;
                    break;
                case 'z':
                    ++totZ;
                    break;


                }//end switch

            }//end while


        }//end while

        System.out.printf("%s%8s\n", "Character", "Total");//column headings

        System.out.println("'A's: " + totA);
        System.out.println("'B's: " + totB);
        System.out.println("'C's: " + totC);
        System.out.println("'D's: " + totD);
        System.out.println("'E's: " + totE);
        System.out.println("'F's: " + totF);
        System.out.println("'G's: " + totG);
        System.out.println("'H's: " + totH);
        System.out.println("'I's: " + totI);
        System.out.println("''J's: " + totJ);
        System.out.println("'K's: " + totK);
        System.out.println("'L's: " + totL);
        System.out.println("'M's: " + totM);
        System.out.println("'N's: " + totN);
        System.out.println("'O's: " + totO);
        System.out.println("'P's: " + totP);
        System.out.println("'Q's: " + totQ);
        System.out.println("'R's: " + totR);
        System.out.println("'S's: " + totS);
        System.out.println("'T's: " + totT);
        System.out.println("'U's: " + totU);
        System.out.println("'V's: " + totV);
        System.out.println("'W's : " + totW);
        System.out.println("'X's: " + totX);
        System.out.println("'Y's: " + totY);
        System.out.println("'Z's: " + totZ);

    }//end main
}//end class

Appears that you are trying to read the parameter from commandline which is not provided.
new FileReader(args[0]) This tries to get the first param passed to the program. If it is not present, then it will throw up the exception. Make sure you pass the file name to the java program as a parameter.

-eNJay

How do i do this?

You should have some txt file (for exapmple). As said eNJay above you should pass file name as a parameter.
You can do it in two ways.
1. Use following:

BufferedReader in =
            new BufferedReader(new FileReader ("test.txt"));

text.txt is your file name.

2. Or you should give your file name as your arg[0]. Put file name while calling -java after classname: java Alphabet test.txt
// this way is better cause you can have different files for which you can use the same program

And one more thing. System.out.printf("%s%8s\n", "Character", "Total");//column headings
Guess this one is from C ;)

Best,
Anna