Sizing problems if instead of ArrayList to manage data, use arrays

Question

What if instead of an ArrayList to manage data, I had to use arrays?

How would I have to manage the growth of this, considering the number of elements can exceed the initial size of the array?

You would have to create a new array with a larger size, then put all the data into the new array — jthort, Nov 01 '16 at 21:44
For what it worth, the source code of `ArrayList` does use an array. — OneCricketeer, Nov 01 '16 at 21:49
Why cant you use ArrayList? Give us a more detailed view of your problem or a context — dodo, Nov 01 '16 at 21:52
Possible duplicate of [Expanding an Array?](http://stackoverflow.com/questions/8438879/expanding-an-array) — jthort, Nov 01 '16 at 21:59

score 0 · Answer 1 · answered Nov 01 '16 at 21:55

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You would need to implement your own ArrayList to do that.

Take a look at what javadoc says about ArrayList:

Resizable-array implementation of the List interface.

answered Nov 01 '16 at 21:55

Leonardo Cruz

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This doesn't answer the question. He is asking how to manage the growth of an array. – jthort Nov 01 '16 at 21:57

score 0 · Accepted Answer · answered Nov 01 '16 at 22:01

You will need to have some sort of heuristics to resize the array. E.g. One of the ideas is to allocate a new array with double the size of the existing array when a new element cannot be added because the array is full. Before you discard the old array, you will need to copy the data from the old array to the new array. Look at Arrays.copyOf to achieve both allocating new array and copying data over.

Yet another alternative is to use a linked list of arrays. Grow the linked list by one every time the existing array is full. This is generally more efficient at runtime because you can resize the array without incurring copying penalty. Of course, it makes the code a tad bit complicated.

Sizing problems if instead of ArrayList to manage data, use arrays

2 Answers2