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I have an array name "asset" with 4 number. I then converted it to be stored in arraylist. Then with the arraylist copy to another array. Is this algorithm correct? After adding 5 the array should be able to show 5 number now

List assetList = new ArrayList();
String[] asset = {"1", "2", "3", "4"}; 

Collections.addAll(assetList, asset);

assetList.add("5");

String [] aListToArray = new String[assetList.size()];
aListToArray.toArray(aListToArray);
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  • 1
    Define correct. What's your actual goal, here? Get a copy of an array? Translate between arrays and ArrayList for an assignment?
    – James
    Commented Sep 27, 2013 at 6:56
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    you can probably do some type safety like List<String> but anyways I am not trying to get why are you coping to a list and copy them back.... had it been a Set I would have understood
    – AurA
    Commented Sep 27, 2013 at 6:57
  • it meets my requirements Commented Sep 27, 2013 at 6:57
  • not assignment but I just want to know if this way of doing is right Commented Sep 27, 2013 at 6:57
  • Why are you using array at all, if the number of elements are varying?
    – Rohit Jain
    Commented Sep 27, 2013 at 6:58

3 Answers 3

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You need to change this line

aListToArray.toArray(aListToArray); // aListToArray to aListToArray itself? This would have given a compilation error

to this

assetList.toArray(aListToArray); // assetList to aListToArray is what you need.
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Use just Arrays.asList(asset);

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You can make some simplifications:

List assetList = new ArrayList();
String[] asset = {"1", "2", "3", "4"}; 

assetList.addAll(asset);

assetList.add("5");

String [] aListToArray = assetList.toArray(aListToArray);

Overall, the code is correct. However if you want to have a "dynamic array", or a collection of items that changes in size, then don't bother trying to keep something in array form. An arraylist will work fine.

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  • how about having first 4 number to be fixed and the rest being dynamically added Commented Sep 27, 2013 at 7:01
  • If you mean having the first 4 values unchangeable, then why would you have them in a collection if you know what they are? What purpose would that be serving?
    – Rogue
    Commented Sep 27, 2013 at 7:03

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