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Thread: Arraylist get problem

  1. #1
    Junior Member
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    Nov 2013
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    Default Arraylist get problem

    Im studying the book programming in BlueJ (Barnes/Kolling 5th ed.) and i am stuck at question 4.51.

    IŽll try to explain:
    There is an arraylist and I must get an object with a specific number, not an indexnumber, but a number which is one of the fields of the objects in the arraylist.

    So the header of the method I am trying to write is:

    Java Code:
    1 public Lot getLot(int lotNumber)

    but the number is an attribute of the objects (Lots) in the arraylist, not the indexnumber. I have no idea how to get the right Lot out of the arraylist. I only know how to access an object in an arraylist via its indexnumber. I hope you can help, I can provide more code from this project if neccesary.
    thanks, Maarten.

  2. #2
    Super Moderator
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    Jun 2013
    So. Maryland, USA
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    Default Re: Arraylist get problem

    So the declaration of your ArrayList<Lot> should look something like:

    List<Lot> lotList = new ArrayList<Lot>();

    Then the lotList is filled with Lot objects:

    lot1 = new Lot();
    lotList.add( lot1 );

    And somewhere in the process of creating an instance of a Lot object or subsequently, the Lot object's field lotNumber is defined. Then to obtain the lotNumber fields of the ArrayList<Lot> lotList, lotList could be iterated or each element of lotList obtained, but an iteration would look like
    for ( Lot lot : lotList )
        System.out.println( "The Lot Number is: " + lot.getLotNumber() );
    Hope this helps. Good luck.

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