Arraylist isnt updating at the right position

Question

Hi all
Im having a problem with arraylist
I have a custom ADT that stores all of my ap data (my stylesheet info)
what i am trying to do is when i click the save changes button, before the changes are saved i am putting my custom ADT into an array list
then i want to be able to traverse back through the arraylist to have an undo feature
however, everytime i add something to my arraylist, everything is becoming the same value
im using ar.add(pointervalue,myadt)
the pointervalue increments when every save is done
is this something to do with me needing to override my equals and hashcode on my custom adt?
i wouldnt expect it to be though as im using an int as my pointer value and not the actual value of the adt (and am i right in thinking arraylist always uses the int pointer as it isnt a map?)
anyway, can anyone help shed a little light on the subject, thanks

Answer 1

as workSheet is defined at the start as it is used in
a few other methods.You have to see the difference between a reference to an object and the object itself.
i can see what your saying, but im not fully
understanding why when i update the worksheet adt,
why isnt it putting it in the arraylist as a new objectBecause this is not PHP, where objects are passed as copies. The list only gets a copy of the reference, not of the object. Both the list and "workSheet" are pointing to the same instance. You use only one instance of your worksheet in your program, that's why anything gets overwritten.
why does the array list update every one?It doesn't. There is only one object, and many references pointing to it.