Homework Help: In Java, should I use a stack when I would normally use an ArrayList?

I'm learning a lot of the Stack data structure, and most importantly, I'm seeing that it can be used to store elements just as any other storage data structure is used.


Now, should I use it instead of an ArrayList, or an Array when the data items are small in nature?

I think this is unconventional, but it is worth a try.

 

Technically a stack can only access data in a first in/last out fashion, like a stack of dishes. That's a pretty serious limitation if you need to get an item from the middle. If you require that type of functionality (like on an undo list) then that is the correct choice.

Not sure about Java's implementation of an ArrayList, but I'm guessing you have more options for accessing its items.

 

Seeing as Stack is LIFO there's only going to be very specific situations where that's ideal (i.e. when implementing a stack). With Arraylist's you can remove and add at specific indexes and it does the resizing etc. for you.

 

I checked the memory usage and time usage of the Stack and ArrayList classes, and got the following numbers on my PC:

Stack: 83 886 000
ArrayList: 70 091 000

The above numbers are the amount of Integer objects that could be added before I got an OoM error.

These are the times I got for the push() and add() methods, respectively.

Median stack time: 583
Median array list time: 582

These numbers were gotten using System.nanoTime(), and taking the median of 101 tries.

As you can see, Stack is a bit more memory efficient in being able to store almost 14 million Integer objects more, while being equally quick in adding new elements.

Overall, I can't say I would recommend using Stack unless it is a natural fit for the task. The trade in flexibility for memory efficiency is not good enough imo.

 

What is the problem?

 

Not really a problem, but more of a general discussion about using Stacks, and ArrayLists.

I'm really liking Stacks, but I tend to forget that each data structure has certain limitations that we must keep in mind.


Thanks for posting.

 

Stacks are like a Pez dispenser