How to get java cpu usage (jvm instance)

Getting cpu usage in java instance, that limits in executing java virtual machine, not os.

Have a look at the java class sun.tools.jconsole.SummaryTab.java in open JDK7 or source in web.(http://www.docjar.com/html/api/sun/tools/jconsole/SummaryTab$Result.java.html)

If you know JConsole, you know that cpu usages graph. that source is below.

354 private static class CPUOverviewPanel extends OverviewPanel {

355 private long prevUpTime, prevProcessCpuTime;

356

357 CPUOverviewPanel() {

358 super(getText("CPU Usage"), cpuUsageKey, cpuUsageName, Plotter.Unit.PERCENT);

359 getPlotter().setDecimals(CPU_DECIMALS);

360 }

361

362 public void updateCPUInfo(Result result) {

363 if (prevUpTime > 0L && result.upTime > prevUpTime) {

364 // elapsedCpu is in ns and elapsedTime is in ms.

365 long elapsedCpu = result.processCpuTime - prevProcessCpuTime;

366 long elapsedTime = result.upTime - prevUpTime;

367 // cpuUsage could go higher than 100% because elapsedTime

368 // and elapsedCpu are not fetched simultaneously. Limit to

369 // 99% to avoid Plotter showing a scale from 0% to 200%.

370 float cpuUsage =

371 Math.min(99F,

372 elapsedCpu / (elapsedTime * 10000F * result.nCPUs));

373

374 getPlotter().addValues(result.timeStamp,

375 Math.round(cpuUsage * Math.pow(10.0, CPU_DECIMALS)));

376 getInfoLabel().setText(getText(cpuUsageFormat,

377 String.format("%."+CPU_DECIMALS+"f", cpuUsage)));

378 }

379 this.prevUpTime = result.upTime;

380 this.prevProcessCpuTime = result.processCpuTime;

381 }

382 }

So. I made my own class to get java-cpu usage.

private void _getJavaRuntime() {

OperatingSystemMXBean osbean = (OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();

RuntimeMXBean runbean = (RuntimeMXBean) ManagementFactory.getRuntimeMXBean();

int nCPUs = osbean.getAvailableProcessors();

long prevUpTime = runbean.getUptime();

long prevProcessCpuTime = osbean.getProcessCpuTime();

try {

Thread.sleep(500);

} catch (Exception e) { }

osbean = (OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();

long upTime = runbean.getUptime();

long processCpuTime = osbean.getProcessCpuTime();

if (prevUpTime > 0L && upTime > prevUpTime) {

long elapsedCpu = processCpuTime - prevProcessCpuTime;

long elapsedTime = upTime - prevUpTime;

javacpu = Math.min(99F, elapsedCpu / (elapsedTime * 10000F * nCPUs));

} else {

javacpu = 0.001;

}

uptime = runbean.getUptime();

}