If you add elements to an array list, one by one, for example:
ArrayList alist = new ArrayList();
alist.add("A");
alist.add("B");
alist.add("C");
alist.add("D");
And then retrieve, say the third element by say, alist.get(2), am I guaranteed to retrieve the third element I added?
Second part of the question, assuming the answer to the first question is yes: When would I use an ArrayList versus a Vector and vice versa.
"Guaranteed"? That's hard to answer, because of the answer to the second part of the question.
ArrayList is not synchronized by default; Vector is.
So if you're running a multi-threaded app, your ArrayList is shared, writable state, and you haven't synchronized properly you might find that guarantee isn't so solid.
If you're running in a single thread, the code you wrote would return "C".
You should still prefer ArrayList, because synchronization is expensive and you might not always want to pay the price.
Yes, you're guaranteed to retrieve the third element you've added.
If you're only working with single-threaded code, use ArrayList. If you need to make sure that the list is thread-safe, use Vector.
Yes, elements are guaranteed to be indexed in the order you added them (much like a primitive array).
You would only use a Vector when absolutely necessary since it is deprecated.
Answer for the first part of your question is yes, you will get "C" .
you should use ArrayList when single thread is manipulating(add/remove) the ArrayList. If two or more threads are manipulating(add/remove) you need to use Vector, as Vector is thread safe I hope this helps
