We had a very ambitious goal of putting quality graphics on an Android device. With Anomaly 2, what were your goals heading into this sequel? You support the squad with extra abilities. This is tower offense game, so it’s a strategy game where you actually attack towers instead of defending them. Initialise an ArrayList like above with a capacity 100 and when you add a breakpoint after that you will see that the internal array has a length of 100.Can you talk about the Anomaly franchise? By doing this you can prevent the internal resizing of the array and items can be added to the ArrayList a lot quicker! This is also a great way to see the effects of the ArrayList being internally an array. This is for the case that you already know or at least have a vague idea how many items you are going to add to the ArrayList. If you do this than the internal array will already be initialised with the capacity you want.
What the ArrayList does in this case is create a new array with twice the size - in our case 8 because the previous size was 4 - and copies all the items from the previous array to the new one: String biggerArray = new String įor(int i = 0 i list = new ArrayList(100) So after adding "a", "b", "c" and "d" the array is full, we cannot add another item to it. We initially just picked a size of 4 for our array. So we continue to add items and they are assigned to the internal array: array = "b" Įverything is fine until "d", but when we want to add "e" we hit a snag. If you were to call size() at this point it would return 1, because there is 1 item in the ArrayList. If you were to place a breakpoint on list.add("b") you would see that the first item in the array is "a" and the 3 spaces after that are null. So after adding "a" we have it at the first position in our array, but the other 3 places are still empty.
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Internally it just assigns this object to one free space in the array, first the "a": array = "a" So now we begin to add items, maybe the letters "a" up to "e": list.add("a") That there are 4 spaces in the array has nothing to do with amount of items actually stored. Because there are no items in the ArrayList. If you called size() now it would return 0.
If you looked at it with a debugger at this time you would see 4 spots in the array of the ArrayList, but all would be null. So what we have now is an ArrayList with 0 items in it, but the array it uses to save those items has already a size of 4. In reality the ArrayList will probably pick a number larger than 4 initially.
The ArrayList does not know at this point how many elements will be added to it, so what is happening internally to the array? When we declare an array it has to have a size, so some arbitrary size is picked, maybe 4: String array = new String Think about when the ArrayList is created: ArrayList list = new ArrayList() To understand the reason you just have to imagine what happens internally in an ArrayList when you add items, I will demonstrate this with a few lines of pseudo code. The answer to that is one simple thing: Performance. You might ask now: "But why is it bigger in the first place?". This is a consequence of how the ArrayList is implemented, as I told you above there is no such thing as a List, the ArrayList is just a wrapper around an array. You are asking why even though size() returns 15 there are 18 elements in the ArrayList when you look at it with the debugger. Stack: Subclass of Vector, but uses a LIFO (Last In, First Out) data structure.Vector: Also uses an array internally, but all operations are synchronised and therefore thread-safe.LinkedList: Holds two references for each element in the list, one to the previous item and one to the next item.ArrayList: Uses an array to store the elements.
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There are multiple classes that implement this List interface and they have different strategies on how to implement it. It contains all the methods which you would expect from a List but there is no default implementation for it. It's always important to remember that List is just an interface.
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