CODEWITHSUNDEEP
javaexceptionindexoutofboundsexception
Violette
Violette

Reputation: 3

Error message: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1

I am in my first class of Java programming and one of the assignments we were given was to create a value string which displays in reverse order separated by commas. I know I am probably missing something very simple, but after hours of trying I just don't know where I am going wrong?

My code works, however I keep getting this error message:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 
    at ip2_jolley.IP2_Jolley.main(IP2_Jolley.java:148) 
Three, Two, One Java Result: 1

This is the code I am using:

String[] f = {"One", "Two", "Three"};
if (f.length > 0) System.out.print (f[2]);
for (int i = 1; i < f.length; i--){
    System.out.print(", " + f[i]); 
}

Upvotes: 0

Views: 401

Answers (3)

ThomasK
ThomasK

Reputation: 155

You start your loop with int i = 1 and then reduce it by 1 every loop which will result in i being lower than 0.

Instead of using int i = 1, you probably want to use int i = f.length

Edit

What you wanted is probably this:

  String[] f = {"One", "Two", "Three","Four","Five"};

    //start at f.length - 1, continue until there is no item left
    for (int i = f.length-1; i >= 0; i--){

        //print current item
        System.out.print(f[i]);

        //if it is not the last item, print separator
        if(i>0){
            System.out.print(", ");
        }
    }
}

Edited with some explanation

Upvotes: 1

Martin Dinov
Martin Dinov

Reputation: 8825

In your code, you start at 1, loop until the length of the array, but decrement i each time. That's a bit mixed up. What you want to do is start at the end of your array (so f.length - 1) and keep moving to the "left" of the array until you are at the beginning of it. So you want this:

for (int i = f.length-1; i >= 0; i--){
   System.out.print(f[i]); 
}

Upvotes: 2

user3504561
user3504561

Reputation: 63

Do you mean:

for (int i = 0; i < f.length; i++)

Instead of:

for (int i = 1; i < f.length; i--)

Upvotes: 0

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