Getting OS memory size from java

Question

Are there any way to get the size of the total memory on the operating system from java? Using

Runtime.getRuntime().maxMemory()

returns the allowed memory for the JVM, not of the operating system. Does anyone have a way to obtain this (from java code)?

@Thorbjørn: If I'm running on a machine with 2GB RAM but the JVM is limited to 1GB, I want to obtain the 2GB size and not the 1GB size returned from the sample code. Or are you asking why I need it? — soren.enemaerke, Dec 02 '10 at 15:21
As part of a library that is to collect some usage statistics (with user consent, of course) — soren.enemaerke, Dec 02 '10 at 17:44

score 17 · Accepted Answer · answered Dec 02 '10 at 13:25

17

com.sun.management.OperatingSystemMXBean bean =
  (com.sun.management.OperatingSystemMXBean)
    java.lang.management.ManagementFactory.getOperatingSystemMXBean();
long max = bean.getTotalPhysicalMemorySize();

returns available RAM size for JVM (limited by 32bit), not the heap size.

answered Dec 02 '10 at 13:25

khachik

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"Access restriction: The type 'OperatingSystemMXBean' is not API" in Java 8, referring specifically to the one in `com.sun.management`. – Brian McCutchon Mar 14 '16 at 03:24

score 3 · Answer 2 · answered Dec 02 '10 at 13:17

3

There is no Java-only way to get that information. You may use Runtime.exec() to start OS-specific commands, e.g. /usr/bin/free on Linux. Still on Linux systems, you can use Java file access classes (FileInputStream) to parse /proc/meminfo.

answered Dec 02 '10 at 13:17

Thomas Pornin

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score 3 · Answer 3 · edited Oct 20 '17 at 15:55

3

that is not possible with pure Java, your program runs on java virtual machine, and therefore it is isolated from OS. I suggest 2 solutions for this:

1) You can use a JNI and call a C++ function to do that
2) Another option is to use Runtime.exec(). Then you have to get the info from "cat /proc/meminfo"

edited Oct 20 '17 at 15:55

Stephan

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answered Dec 02 '10 at 13:20

Caner

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score 0 · Answer 4 · answered Aug 12 '21 at 13:58

You can get the RAM usage with this. This is the same value that taskmanager in windows shows

    com.sun.management.OperatingSystemMXBean bean = (com.sun.management.OperatingSystemMXBean)java.lang.management.ManagementFactory.getOperatingSystemMXBean();
    double percentage = ((double)bean.getFreeMemorySize() / (double)bean.getTotalPhysicalMemorySize()) * 100;
    percentage = 100 - percentage;
    System.out.println("RAM Usage: " + percentage + "%");

Getting OS memory size from java

4 Answers4

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