Trying to calculate average but I get the error: java.lang.IndexOutOfBoundsException: Index: 1, Size: 1

Question

I am trying to create a function to calculate an average, but I keep getting an error message, which is really frustrating because I know it is a super easy function. I keep getting the error java.lang.IndexOutOfBoundsException so I know it has something to do with an index error but I can't figure it out.

public int berekenGemiddeldeScore(){

    int result = 0;
    int i = 0;

    if (deelnemers.size() == 1){

        return deelnemers.get(1).getScore();
    }

    while (i< deelnemers.size() -1 ){

        result+=deelnemers.get(i).getScore();
        i++;
    }

    return result/deelnemers.size();

}

Yeah sorry lol I accidently entered before I finished my question. — RandomStacker, Apr 19 '17 at 17:00
```if (deelnemers.size() == 1){ return deelnemers.get(1).getScore(); }``` if that condition is met... the only index should be... 0 right, not 1? — David Espino, Apr 19 '17 at 17:01
If size is 1, index should be 0. counting starts at 0, 1, 2...N-1 where n is the size. — Alex, Apr 19 '17 at 17:03
@RandomStacker what is the type of `deelneimers`? Is it List>? — djm.im, Apr 19 '17 at 17:08
Whoops, the dupe is about `ArrayIndexOutOfBoundException`, but they're pretty much the same thing. — Kayaman, Apr 19 '17 at 17:09
@RandomStacker I updated my answer. there is no reason to have special case when the list has size 1. — djm.im, Apr 19 '17 at 17:15

score 0 · Answer 1 · answered Apr 19 '17 at 17:03

In Java and many other languages the first index is 0, not 1. In your case the collection has size 1, so the only index you can access using get is 0: deelnemers.get(0).

If you try to access using an index that does not exist in the collection, an exception of type IndexOutOfBoundsException is thrown.

score 0 · Answer 2 · answered Apr 19 '17 at 17:03

Replace your code with this-

public int berekenGemiddeldeScore(){

int result = 0;
int i = 0;

if (deelnemers.size() == 1){
    return deelnemers.get(0).getScore();
}

while (i < deelnemers.size()){

    result+=deelnemers.get(i).getScore();
    i++;
}

return result/deelnemers.size();
}

score 0 · Answer 3 · answered Apr 19 '17 at 17:03

0

If you have an array with only one item, "if (deelnemers.size() == 1)" the index of your array is 0:

return deelnemers.get(0).getScore();

answered Apr 19 '17 at 17:03

rodrigo

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djm.im · Answer 4 · 2017-04-19T17:13:41.007

This is the issue

if (deelnemers.size() == 1) {
    return deelnemers.get(1).getScore();
}

Replace return statement with

 return deelnemers.get(0).getScore();

Edit

There is no reason for a special case if list size is one. Think about this approach

public int berekenGemiddeldeScore() {
    if (deelnemers.size() == 0) {
        return 0;
    }

    int result = 0;
    for (Score score : deelnemers) {
        result += score.getScore();
    }

    return result / deelnemers.size();
}

Trying to calculate average but I get the error: java.lang.IndexOutOfBoundsException: Index: 1, Size: 1

4 Answers4