Java ArrayIndexOutOfBoundsException and I don't know why or what to do

Question

public void addTransaction(Transaction t){
    mSize++;
    Transaction[] temp = new Transaction[mSize];
    System.arraycopy(mTransactions, 0, temp, 0, mSize - 1);
    temp[-1] = t // ERROR HERE
    mTransactions = temp;
}

temp[-1] should replace the last element of temp, which is empty, with the passed argument t, but instead errors.

As long as temp's size is greater than 1, this exception shouldn't happen right? All it's trying to do is modify the last element.

Being new to a language isn't an excuse for not familiarizing yourself with the basics. — Bill the Lizard, Sep 04 '16 at 22:19
It's not really a duplicate. The code is correct, as is OP's understanding of AIOOBE, except for a small typo or misunderstanding. — shmosel, Sep 04 '16 at 22:41

score 3 · Answer 1 · answered Sep 04 '16 at 22:16

3

-1 is an invalid array index. If you're trying to set the last element, it should be

temp[temp.length-1] = t;

answered Sep 04 '16 at 22:16

shmosel

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I have a little background in python, hence the [-1]. Thanks for your help. – MaxG Sep 04 '16 at 23:06

Java ArrayIndexOutOfBoundsException and I don't know why or what to do

1 Answers1