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convert String arraylist to string array in java?

Following is my code

ArrayList<String> IdList = new ArrayList<String>();

and I want to copy items from IDList to int IdArray[].

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int[] or String[] array? – Prince John Wesley Oct 14 '11 at 9:05
Actually i want it int array. but String[] is also fine. – Soniya Oct 14 '11 at 9:06
You should start with an ArrayList<int> in the first place if it doesn't matter XD – Rob Oct 14 '11 at 9:08
@ All: Thanks for your help. Following code helped me out String[] array = Idlist.toArray(new String[list.size()]); – Soniya Oct 14 '11 at 10:08
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marked as duplicate by aioobe, Reno, Lord Torgamus, Octavian Damiean, Graviton Oct 19 '11 at 2:51

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6 Answers

up vote 0 down vote 
int[] IdArray = IdList.toArray();

However, this will probably fail because you're trying to convert a string-arraylist to an int-array..

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up vote 0 down vote

I think you must iterate through all items, which are Strings, and parse each of them into an int to populate your new int[] array.

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Did you mean, Iterator itr = IdList.iterator(); int IdArray[]={}; int d=0; while(itr.hasNext()) { String topic_id = (String) itr.next(); IdArray[d]= Integer.parseInt(topic_id); d++; System.out.print("============"+topic_id ); } – Soniya Oct 14 '11 at 9:11
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up vote 0 down vote 
// String array
String[] arr = idList.toArray(new String[0]);
// for int array
int[] iarr = new int[arr.length];
int idx = 0;
for(String s : arr) {
   iarr[idx++] = Integer.parseInt(s);
}
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up vote 2 down vote

String [] outStrArray = (String [])IdList.toArray()

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This will throw a ClassCastException because Collection.toArray() returns a Object[]. – x4u Oct 14 '11 at 9:28
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up vote 5 down vote

Try this stuff,

     int arr[] = new int[arrList.size()];
        for (int i = 0; i < arrList.size(); i++) {
            arr[i] = Integer.parseInt(arrList.get(i));
        }
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gave ArrayIndexOutOfBoundException – Soniya Oct 14 '11 at 9:40
int asize= IdList.size(); int arr[] = new int[asize]; for (int i = 0; i < asize); i++) { arr[i] = Integer.parseInt(IdList.get(i)); } – Soniya Oct 14 '11 at 10:00
@ Lalit: Thanks. I got the solution. – Soniya Oct 14 '11 at 10:43
let us continue this discussion in chat – Soniya Oct 14 '11 at 10:43
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up vote 0 down vote 
ArrayList<String> IdList = new ArrayList<String>();
int IdArray[].
    for (int i = 0; i < IdList.size(); i++) {
        IdArray[i] = (int)IdList.get(i));
    }
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