获取运行时JVM可用的内存 [英] Obtaining memory available to JVM at runtime

问题描述

我正在尝试对一堆数据进行排序，以便输入到程序的数据大小可以大于JVM可用的内存，并且处理需要外部排序，这比Quicksort慢得多。

I'm trying to sort a bunch of data such that that the size of data input to the program can be larger than the memory available to the JVM, and handling that requires external sort which is much slower than Quicksort.

有没有办法在运行时获取JVM可用的内存，这样我就可以尽可能地使用就地排序，只在数据输入太大时切换到Mergesort ？

Is there any way of obtaining memory available to the JVM at runtime such that I could use in place sorting as much as possible, and only switch to Mergesort when data input is too large?

推荐答案

在 java.lang.Runtime class：

Check out these methods on the java.lang.Runtime class:

freeMemory

totalMemory

maxMemory

示例

Runtime rt = Runtime.getRuntime();
System.err.println(String.format("Free: %d bytes, Total: %d bytes, Max: %d bytes",
  rt.freeMemory(), rt.totalMemory(), rt.maxMemory()));

另请注意，如果内存总量耗尽，您始终可以使用更大的内存启动JVM使用 -Xmx JVM参数分配的堆量;例如

Also note that if the total amount of memory is being exhausted you can always start the JVM with a larger amount of heap allocated using the -Xmx JVM argument; e.g.

java -Xmx256M MyClass

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