ArrayList insertion and retrieval order

Question

Suppose I insert 5 strings in an ArrayList  Will the order of insertion and retrieval from the ArrayList be the same

User · Answer

Yes  it will always be the same  From the documentation     Appends the specified element to the end of this list  Parameters  e   element to be appended to this list Returns  true  as specified by   Collection add java lang Object     ArrayList add   implementation  public boolean More    add E e        ensureCapacity size   1       Increments modCount       elementData size      e      return true

User · Answer

Yes  ArrayList is a sequential list  So  insertion and retrieval order is the same   If you add elements during retrieval  the order will not remain the same

User · Answer

If you always add to the end  then each element will be added to the end and stay that way until you change it   If you always insert at the start  then each element will appear in the reverse order you added them   If you insert them in the middle  the order will be something else

User · Answer

Yes it remains the same  but why not easily test it  Make an ArrayList  fill it and then retrieve the elements

User · Answer

Yes  ArrayList is an ordered collection and it maintains the insertion order  Check the code below and run it  public class ListExample        public static void main String   args            List lt String gt  myList   new ArrayList lt String gt             myList add  quot one quot            myList add  quot two quot            myList add  quot three quot            myList add  quot four quot            myList add  quot five quot                 System out println  quot Inserted in  order    quot            printList myList           System out println  quot  n quot            System out println  quot Inserted out of  order    quot                Clear the list         myList clear                 myList add  quot four quot            myList add  quot five quot            myList add  quot one quot            myList add  quot two quot            myList add  quot three quot                 printList myList              private static void printList List lt String gt  myList            for  String string   myList                System out println string                      Produces the following output  Inserted in  order    one two three four five   Inserted out of  order    four five one two three  For detailed information  please refer to documentation  List  Java Platform SE7

[java] ArrayList insertion and retrieval order

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