Re: list of arrays
"Eric Sosman" <Eric.Sosman@sun.com> wrote in message
news:1167766532.942789@news1nwk...
Jeremy Watts wrote On 01/02/07 13:24,:
I have created a List with the intention of putting elements of
one-dimensional arrays within it. The arrays contain integers. The
lines
I've used are:-
(for the purposes of this, I have set variableNumber equal to 5)
List<int[]>combinationList = new ArrayList<int[]>();
int[] degrees = new int[variableNumber + 1];
{ some routine which fills each element of 'degrees' with a random
integer}
then, I wish to add the newly filled 'degrees' to the end of the list,
using
:-
combinationList.add(degrees);
theres no problem just doing this the once, but if I attempt to add
another
instance of 'degrees' to the list using the same above statement, then
it
seems to overwrite the initial instance of degrees with the new one.
Why is it doing this? I cant seem to find a way around it. If I run
through say 10 iterations of the above then I am simply left with a list
of
10 arrays all of which are identical to the last generated instance of
'degrees'.
You are probably doing this:
int[] degrees = new int[variableNumber + 1];
for (int i = 0; i < 10; ++i) {
// fill degrees[] with data
combinationList.add(degrees);
}
... when you ought to be doing this:
for (int i = 0; i < 10; ++i) {
int[] degrees = new int[variableNumber + 1];
// fill degrees[] with data
combinationList.add(degrees);
indeed i was.... shortly discovered after posting this :) thanks for the
reply anyway
}
The first version creates one array, fills it with numbers
adds it to the List, re-fills the exact same array with another
batch of numbers, adds it to the List a second time, ... At
the end, there's still only one array and it contains only the
last set of values you placed in it. Oh, and that same array
appears ten times in the List.
The second version creates an array, fills it with numbers
and adds it to the List, then creates a second array, fills that
array with numbers and adds it to the List, ... At the end,
there are ten independent arrays, each with its own set of
values, and each appearing once in the List.
If that's not the problem, please post a short, complete
example that demonstrates your difficulty.
--
Eric.Sosman@sun.com