java.lang.ArrayIndexOutOfBoundsException:10 even though the array can go up to 10

Question

I'm getting a "java.lang.ArrayIndexOutOfBoundsException:10" error on my "if" statement even though the file im getting the data from has an index enough to be 10.

When I call info[10] in other places in my code it works but i dont know why it's not working here.

learning file management unit in computer science right now...

public static void comSci(String onTheMap) throws IOException  
{         
    BufferedReader input = new BufferedReader (new FileReader ("data.txt"));
    if (onTheMap.equals("3")){    
        Scanner scanner = new Scanner("data.txt");
        String line="x";
        System.out.println("--------------------------------------------------------------");
        System.out.println("Create a file of student's who are enrolled in ICS3U0:");
        System.out.println("--------------------------------------------------------------");
        String info[] = new String[20];
        boolean finder = false;      

        while (line!=null) {
            line = input.readLine();
            if (line==null)
                break;        
            info = line.split(",");

            if (info[10].toLowerCase().contains("ICS3U0".toLowerCase())) {  //PROBLEM
                finder = true;
                String programmers = info[0] + "," + info[1];
                System.out.println(programmers);
                try {
                    FileWriter theFile = new FileWriter("ICS3U0.txt",true);
                    PrintWriter names = new PrintWriter(theFile);
                    names.println();
                    names.close();

                }
                catch (FileNotFoundException e) {
                    e.printStackTrace();
                }
            }  
        } 
        System.out.println("ICS3U0.TXT WAS CREATED");

    }
    input.close();

}

Arrays are 0-indexed in Java, so a size 10 array has legal indexes of 0-9. 10 is out of bounds. — azurefrog
– azurefrog, Commented Dec 16, 2014 at 22:09
Check the length of line.split(",");. If you are sure that there should be at least 11 elements, then there's something wrong with your input data. — Alexis C.
– Alexis C., Commented Dec 16, 2014 at 22:10
@MatthewLogique That's not possible, otherwise you wouldn't have this exception. — Alexis C.
– Alexis C., Commented Dec 16, 2014 at 22:12
Check for info.length > 10 before you try to access info[10]. I guarantee the array is smaller than you think. Also, you should update the title of your question, it is misleading. — azurefrog
– azurefrog, Commented Dec 16, 2014 at 22:13
@LeTex No, don't do that. That would just hide whatever bug is causing it to be less than 10. He needs to find out what's happening, rather than sticky-taping over the problem. This is what a debugger is for. — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Dec 16, 2014 at 22:16

Elliott Frisch · Accepted Answer · 2014-12-16 22:09:50Z

2

Java array indexes start at 0. So an array of length 10 has valid indexes from 0-9 inclusive (or 0-10 exclusive). This is why the for loop is usually styled,

for (int i = 0; i < arr.length; i++) { // <-- less than (not less than =).
   // ...
}

answered Dec 16, 2014 at 22:09

Elliott Frisch

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2 Comments

MatthewLogique Over a year ago

That wasn't the problem

Dawood ibn Kareem Over a year ago

Yes it was. The fact that LeTex's advice worked for you PROVES that it was.

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