Creating a huge 2D array in Java

Question

I am trying to create a huge 2D array.

String[][] arr = new String[100000][100000];

But on execution, I get java.lang.OutOfMemoryError: Java heap space

Other than increasing my heap space, how do I prevent getting this exception?

What is your data source? Do you really need all the data at the same time for processing? Otherwise you should consider writing data to a file, to free up space, adapt your processing algorithms to work on data batches, filter while writing, etc. — Frederic Klein
– Frederic Klein, Commented May 7, 2016 at 6:49
Do you actually have that much RAM? If yes, you can try to increase the heap size -Xmx20g, see stackoverflow.com/questions/14763079/… But you should consider, that this won't be very fast. You should consider using a different algorithm or some kind of distributed cache / in memory DB. — Moritz Petersen
– Moritz Petersen, Commented May 7, 2016 at 6:58
@Mortiz Can you suggest an alternate algorithm for storing the huge data? — Arun George
– Arun George, Commented May 7, 2016 at 9:47

karthikdivi · Accepted Answer · 2016-05-07 05:45:14Z

1

Are you really going to use 100000 X 100000 positions, If not and you are not sure about the max limit you can start with List of Lists

declare like this List<List<String>> arr = new ArrayList<List<String>>();

When ever you want to call you need to do this arr.get(0).get(1); instead arr[0][1]

answered May 7, 2016 at 5:45

karthikdivi

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1 Comment

I am sure about the max limit. I can use a list, but while inserting, at some point, I would again end up out of memory.

Florent TESTE · Accepted Answer · 2016-05-07 06:44:37Z

1

You can't do that Oo It make 100000*100000 = 10.000.000.000 datas for your array !

You are out of your memory !!

Reduce the two number, i don't think that you need this much memory !

You can go on a :

String[][] arr = new String[14000][14000];

I tried and it works !

answered May 7, 2016 at 6:25

Florent TESTE

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