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Thread: converting array into arraylist

  1. #1
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    Default converting array into arraylist

    Currently i have:
    int[] test = {1,2,3,4,5};
    ArrayList<Integer> ar = new ArrayList<Integer>(Arrays.asList(test));

    this gives me the error:
    error: no suitable constructor found for ArrayList(List<int[]>)
            ArrayList<Integer> ar = new ArrayList<Integer>(Arrays.asList(test));
                                    ^
        constructor ArrayList.ArrayList(Collection<? extends Integer>) is not applicable
          (actual argument List<int[]> cannot be converted to Collection<? extends Integer> by method invocation conversion)
        constructor ArrayList.ArrayList() is not applicable
          (actual and formal argument lists differ in length)
        constructor ArrayList.ArrayList(int) is not applicable
          (actual argument List<int[]> cannot be converted to int by method invocation conversion)
    1 error

    What i want to do is make a method that takes an array as parameter and returns an arraylist with the same elements.


  2. #2
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    Default Re: converting array into arraylist

    See the API for Arrays.asList...it accepts an array of objects - not primitives (in many cases the compiler is smart enough to interchange through something called autoboxing - in this case not). Using a simple loop you can add the items of the array to the List.

  3. #3
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    Default Re: converting array into arraylist

    bleh, thanks anyway

  4. #4

    Default Re: converting array into arraylist

    Create the method yourself. Just iterate through the array and return the elements in a new list.

    public ArrayList<T> arrayToArrayList(<T> array)
    {
         ArrayList<T> list = new ArrayList<T>();
         for(int i=0; i<array.length; i++)
              list.add(array[i]);
         return list;
    }
    Kenneth Walter
    Software Developer
    http://kennywalter.com

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    Default Re: converting array into arraylist

    Quote Originally Posted by Harry Blargle View Post
    What i want to do is make a method that takes an array as parameter and returns an arraylist with the same elements.
    Then do what kenster421 said. Iterate through the array and add it all to the ArrayList.

    One small fix though. Make the parameter an "E" array. (E[] array)

    public ArrayList<E> test(E[] array) {
        //Iterating code
    }

    Be careful when using generic types with plain arrays though. They hold primitives as well as objects, which can cause problems.

  6. The Following User Says Thank You to bgroenks96 For This Useful Post:

    kenster421 (October 6th, 2011)

  7. #6

    Default Re: converting array into arraylist

    Quote Originally Posted by bgroenks96 View Post
    Then do what kenster421 said. Iterate through the array and add it all to the ArrayList.

    One small fix though. Make the parameter an "E" array. (E[] array)

    public ArrayList<E> test(E[] array) {
        //Iterating code
    }

    Be careful when using generic types with plain arrays though. They hold primitives as well as objects, which can cause problems.
    Whoops, thanks for the clarification.
    Kenneth Walter
    Software Developer
    http://kennywalter.com

  8. #7
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    Default Re: converting array into arraylist

    Hi,
    You have to use:
    Integer[] test for this.

    bean factory
    Last edited by abani; December 18th, 2011 at 01:00 AM.

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