file input: array of integers

[hannes]

Hey guys,

I want to read an array of integers from a txt file, but before i can read the array i have to initialize the array of integers. How can i do this that the array is not to big? I've tried so far with the lenght( ) method of my file object, but my array was too big. Has anyone got a solution?

Thanks, Hannes

[pbrockway2]

Either read the file twice, the first time to determine exactly how many integers it contains and the second time to actually read the data once the array has been created. Or use a collection that grows as needed: List<Integer> has an add() method and, unlike an array, it just gets as big as needed.

I know you said "I want to read an array..." but consider not doing that. Perhaps you can do whatever processing you need without holding all of the integers in memory at the same time.

[hannes]

It is for drawing a curve, so i have to hold the array in memory.

I've an array of 20.000 integers. One integer takes 4 bytes, that's 80.000 bytes totally. And i want 100 arrays: 100*80000=8.000.000 bytes= 8.000kb=8mb only. That's not that much.

[Tolls]

Why do you have to hold it in memory though?

[hannes]

you can modify the arrays, change colors and so on...

Hannes

[Tolls]

OK.
Then do one of the suggestions above, either two read throughs, one to find the length and the other to actually read the data...or List<Integer> (or List<Integer>[100]). Note that List<Integer> will require more memory, but that should still not prove a problem.

[Spike_CT]

I agree with Tolls.

If you use the List<Integer>, you can use List.toArray() once the List is filled to get an Integer array. The List can then be discarded and you can continue with the array. This could prove handy when performance or memory are important.

[hannes]

Great, thanks guys!

Hannes

[Tolls]

Well, to be fair it wasn't my suggestion...:)