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A very simple problem with ArrayList<int[]> 2

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lellus

Technical User
Apr 25, 2009
2

Hi. I don't understand this strange behaviour.

import java.util.ArrayList;

public class Main {

public static void main(String[] args) {

int[] number = null;
ArrayList<int[]> numbers = null;

number = new int[1];
numbers = new ArrayList<int[]>();

for ( int value = 0; value<10 ; value++){
number[0] = value;
System.out.println(number[0]);
numbers.add(number);
}

//Output 0 1 2 3 4 5 6 7 8 9

for (int index = 0; index<numbers.size(); index++){
System.out.println(numbers.get(index)[0]);
}

//Output 9 9 9 9 9 9 9 9 9 9
}

Why the second output is different, why i have no store the sequence of numbers into Arraylist as vectors of integers?
Thanks
 
Arrays are reference types. So after the first loop, your arraylist will contain ten references to the same array.
 
The entries would reference the same object which finally settled in number[0]=9. Had only its clone be added each time, it wouldn't be the same.
>numbers.add(number);
[tt]numbers.add(number[blue].clone()[/blue]);[/tt]
 
yes yes yes
I'm very stupid!!
Thank you
 
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