Silly trouble
Hi friends i've a newbie's trouble.....
i've this simply code to create a disposition on n variables....
publicclass Main{
staticint posiz = 0;
static ArrayList app_arr;
static ArrayList dispo;
staticint numsol = 0;
publicstaticvoid main(String[] args){
app_arr =new ArrayList();
for (int i = 0; i < 10; i++){
app_arr.add(i, 0);
}
dispo =new ArrayList();
disposition(10);
ArrayList app2 =new ArrayList();
for (int i = 0; i < dispo.size(); i++){
System.out.println(dispo.get(i));
}
}
publicstaticvoid disposition(int length){
int bit = 0;
do{
app_arr.set(posiz, bit);
posiz++;
if(posiz==length){
//System.out.print(app_arr);
dispo.add(numsol, app_arr);
numsol++;
System.out.println("Disposizione numero "+numsol);
}
else{
disposition(length);
}
posiz--;
bit++;
}
while(bit<2);
}
}
but when i print the dispo ArrayList there is always the same (the last) disposition!!....why? how i can solve this problem?...thanks
I don't have my Italian dictionary at hand. My English dictionary translates "disposition" as "(natural) bent", "inclination" or "arrangement", neither of which is precise enough for me to make sense of what you're saying. So please explain more clearly.
You're code looks confusing to me, especially the recursion controlled by a global variable (posiz). You may consider starting over with clearer code.
I don't know the correct translation but i can make you a example.....
If i want the disposition of 3 bit variables the result will be:
000
001
010
011
100
101
110
111
This code is quite correct because it creates well the "dispositions" (sorry but i don't know the real name in english!) into arr_app but it doesn't save well them into the second ArrayList dispo.
It puts always the last disposition which is founded!!
Now it's clear to me what you want to do.
I'm still having trouble reading your code. However, I agree that recursion is warranted.
Could it be this?
dispo.add(numsol, app_arr);
You add the app_arr ArrayList as an element to your dispo ArrayList. However, you add the same ArrayList object every time, so dispo ends up holding several references to the same ArrayList. This would explain why every entry seems to hold the last disposition created (let's just call them dispositions until someone may propose a better term; it seems to agree with the translation as "arrangement").
Instead you need to add a copy of ap_arr to dispo.
Message was edited by:
OleVV
dispo = new ArrayList(); // now dispo points to another (empty) ArrayList - original list is gone
disposition(10);// method call adds stuff to the new (empty) ArrayList
If you want to keep adding elements to dispo, don't instantiate a new one each time.
static ArrayList dispo = new ArrayList(); // created just once at class level
As for app_arr, you're creating a new one each time, and filling it with the same elements. ..? Use a static initializer.
