jmx - How to get percentage of CPU usage of OS from java

Question

I want to calculate percentage of CPU usage of OS from java code.

1. There are several ways to find it by unix command [e.g. using mpstat, /proc/stat etc...] and use it from Runtime.getRuntime().exec

But I don't want to use the system calls.

I tried ManagementFactory.getOperatingSystemMXBean()

OperatingSystemMXBean osBean =
         (OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
System.out.println(osBean.getSystemLoadAverage());

But it gives the cpu load but not the cpu usage. Is there anyway to find the usage percentage?

Answer 1

In Java 7 you can get it like so:

public static double getProcessCpuLoad() throws Exception {

    MBeanServer mbs    = ManagementFactory.getPlatformMBeanServer();
    ObjectName name    = ObjectName.getInstance("java.lang:type=OperatingSystem");
    AttributeList list = mbs.getAttributes(name, new String[]{ "ProcessCpuLoad" });

    if (list.isEmpty())     return Double.NaN;

    Attribute att = (Attribute)list.get(0);
    Double value  = (Double)att.getValue();

    // usually takes a couple of seconds before we get real values
    if (value == -1.0)      return Double.NaN;
    // returns a percentage value with 1 decimal point precision
    return ((int)(value * 1000) / 10.0);
}