Java内存不足2D阵列 [英] Java Out of memory 2D Array

问题描述

我正尝试如下创建2D数组.

I am trying to create a 2D array as below.

int NUM_RECORDS = 100480507;

byte[][] completeArray = new byte[NUM_RECORDS][6];

拥有100480507 * 6 ~= 0.6 GB

请参见> 此 问题.

See this question as well.

但是此数组的创建将耗尽内存.我已经通过JVM args为我的java进程分配了4G.

But creation of this array runs out of memory. I have allocated 4G to my java process through JVM args.

如何解释?我在这里想念一些琐碎的东西吗?

How can that be explained? I am I missing some thing trivial here?

这是我的程序

public class MemTest {

   public static void main(String[] args) {
       int NUM_RECORDS = 100480507;
       byte[][] completeArray = new byte[NUM_RECORDS][6];
       System.out.println("Array created");
   }
}

推荐答案

每个数组都有开销(例如，有关开销，请参阅IBM文档->

Each array has an overhead (for example, see IBM documentation on their overhead -> http://www.ibm.com/developerworks/java/library/j-codetoheap/index.html). In your case, you are creating 100480507 of them!

如果您将代码更改为" byte [] completeArray = new byte [ NUM_RECORDS * 6 ];"，则根据您的理论，它应该占用相同的空间！但是，我相当确定这会起作用，因为开销最少.您也可以尝试"byte [] [] completeArray = new byte [6] [NUM_RECORDS] ;".而且应该也可以(减少开销).

If you change your code to "byte[] completeArray = new byte[NUM_RECORDS*6];", according to your theory, it should demand the same space! But, I am fairly certain this will work as there is least overhead. You could also try "byte[][] completeArray = new byte[6][NUM_RECORDS];" and that should work too (lesser overhead).

我知道这不会解决您的问题-但我希望这可以使您对间接费用有所了解.

I know this will not solve your issue - but I hope this will give you some perspective on the overhead.

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