Java memory usage by array objects

Question

How many heap space takes array object? I mean not a array reference. For example how many heap space will take this array

Integer[] array = new Integer[5];

Or perhaps you know some ways how I can to test memory usage of my application? Any suggestions and advices will be appreciated)

Thanks in advance!

Have you ever seen [this?](http://stackoverflow.com/help/how-to-ask) — Jude Niroshan, Apr 15 '15 at 19:27
If you want to read the layout of a given object and its size you could use [JOL](http://openjdk.java.net/projects/code-tools/jol/). — eckes, Apr 15 '15 at 21:09
@eckes thanks for your comment, as far as I see this thing is suitable for my purpose (wow it show how many space each Object use and many other interesting information) — Mike Herasimov, Apr 16 '15 at 05:44

score 1 · Answer 1 · answered Apr 15 '15 at 19:34

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It depends if the array is of primitive type of object types. If it is int[] = new int[5] it will be 5 times int memory size - 5x4=20 bytes.

If it is Object and not primitive like in your case (Integer) then the memory used is the number of the object multiplied by reference memory size ( the pointer size ) - 32 bits or 64 bits depending on the JVM.

answered Apr 15 '15 at 19:34

Veselin Davidov

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An array has a type pointer and size field in addition to the actual elements, so it is typically (count+1)*oopsize + intsize. – eckes Apr 15 '15 at 21:08

score -1 · Answer 2 · edited May 23 '17 at 12:22

-1

I believe you mean:

Integer[] array = new Integer[5];

And integers are 4 bytes when being used... so 4*5= 20 bytes. But there is more to it than just this.. Certain overhead on the array's in such and the fact you are using the Integer class rather than just doing:

int[] array = new int[5];

I would suggest trying to google for a more explained answer or go here: Calculating Java Array Memory Usuage

edited May 23 '17 at 12:22

Community

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answered Apr 15 '15 at 19:25

user2494817

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@eckes Yes... I shortly explained that in my answer... – user2494817 Apr 16 '15 at 00:25

Java memory usage by array objects

2 Answers2