How do I monitor the computer's CPU, memory, and disk usage in Java?

Along the lines of what I mentioned in this post. I recommend you use the SIGAR API. I use the SIGAR API in one of my own applications and it is great. You'll find it is stable, well supported, and full of useful examples. It is open-source with a GPL 2 Apache 2.0 license. Check it out. I have a feeling it will meet your needs.

Using Java and the Sigar API you can get Memory, CPU, Disk, Load-Average, Network Interface info and metrics, Process Table information, Route info, etc.

The following supposedly gets you CPU and RAM. See ManagementFactory for more details.

import java.lang.management.ManagementFactory;
import java.lang.management.OperatingSystemMXBean;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

private static void printUsage() {
  OperatingSystemMXBean operatingSystemMXBean = ManagementFactory.getOperatingSystemMXBean();
  for (Method method : operatingSystemMXBean.getClass().getDeclaredMethods()) {
    method.setAccessible(true);
    if (method.getName().startsWith("get")
        && Modifier.isPublic(method.getModifiers())) {
            Object value;
        try {
            value = method.invoke(operatingSystemMXBean);
        } catch (Exception e) {
            value = e;
        } // try
        System.out.println(method.getName() + " = " + value);
    } // if
  } // for
}

In JDK 1.7, you can get system CPU and memory usage via com.sun.management.OperatingSystemMXBean. This is different than java.lang.management.OperatingSystemMXBean.

long getCommittedVirtualMemorySize()
// Returns the amount of virtual memory that is guaranteed to be available to the running process in bytes, or -1 if this operation is not supported.

long getFreePhysicalMemorySize()
// Returns the amount of free physical memory in bytes.

long getFreeSwapSpaceSize()
// Returns the amount of free swap space in bytes.

double getProcessCpuLoad()
// Returns the "recent cpu usage" for the Java Virtual Machine process.

long getProcessCpuTime()
// Returns the CPU time used by the process on which the Java virtual machine is running in nanoseconds.

double getSystemCpuLoad()
// Returns the "recent cpu usage" for the whole system.

long getTotalPhysicalMemorySize()
// Returns the total amount of physical memory in bytes.

long getTotalSwapSpaceSize()
// Returns the total amount of swap space in bytes.

This works for me perfectly without any external API, just native Java hidden feature :)

import com.sun.management.OperatingSystemMXBean;
...
OperatingSystemMXBean osBean = ManagementFactory.getPlatformMXBean(
                OperatingSystemMXBean.class);
// What % CPU load this current JVM is taking, from 0.0-1.0
System.out.println(osBean.getProcessCpuLoad());

// What % load the overall system is at, from 0.0-1.0
System.out.println(osBean.getSystemCpuLoad());

Have a look at this very detailled article: http://nadeausoftware.com/articles/2008/03/java_tip_how_get_cpu_and_user_time_benchmarking#UsingaSuninternalclasstogetJVMCPUtime

To get the percentage of CPU used, all you need is some simple maths:

MBeanServerConnection mbsc = ManagementFactory.getPlatformMBeanServer();

OperatingSystemMXBean osMBean = ManagementFactory.newPlatformMXBeanProxy(
mbsc, ManagementFactory.OPERATING_SYSTEM_MXBEAN_NAME, OperatingSystemMXBean.class);

long nanoBefore = System.nanoTime();
long cpuBefore = osMBean.getProcessCpuTime();

// Call an expensive task, or sleep if you are monitoring a remote process

long cpuAfter = osMBean.getProcessCpuTime();
long nanoAfter = System.nanoTime();

long percent;
if (nanoAfter > nanoBefore)
 percent = ((cpuAfter-cpuBefore)*100L)/
   (nanoAfter-nanoBefore);
else percent = 0;

System.out.println("Cpu usage: "+percent+"%");

Note: You must import com.sun.management.OperatingSystemMXBean and not java.lang.management.OperatingSystemMXBean.

The accepted answer in 2008 recommended SIGAR. However, as a comment from 2014 (@Alvaro) says:

Be careful when using Sigar, there are problems on x64 machines... Sigar 1.6.4 is crashing: EXCEPTION_ACCESS_VIOLATION and it seems the library doesn't get updated since 2010

My recommendation is to use https://github.com/oshi/oshi

Or the answer mentioned above.

For disk space, if you have Java 6, you can use the getTotalSpace and getFreeSpace methods on File. If you're not on Java 6, I believe you can use Apache Commons IO to get some of the way there.

I don't know of any cross platform way to get CPU usage or Memory usage I'm afraid.

A lot of this is already available via JMX. With Java 5, JMX is built-in and they include a JMX console viewer with the JDK.

You can use JMX to monitor manually, or invoke JMX commands from Java if you need this information in your own run-time.

/* YOU CAN TRY THIS TOO */

import java.io.File;
 import java.lang.management.ManagementFactory;
// import java.lang.management.OperatingSystemMXBean;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.lang.management.RuntimeMXBean;
 import java.io.*;
 import java.net.*;
 import java.util.*;
 import java.io.LineNumberReader;
 import java.lang.management.ManagementFactory;
import com.sun.management.OperatingSystemMXBean;
import java.lang.management.ManagementFactory;
import java.util.Random;



 public class Pragati
 {

     public static void printUsage(Runtime runtime)
     {
     long total, free, used;
     int mb = 1024*1024;

     total = runtime.totalMemory();
     free = runtime.freeMemory();
     used = total - free;
     System.out.println("\nTotal Memory: " + total / mb + "MB");
     System.out.println(" Memory Used: " + used / mb + "MB");
     System.out.println(" Memory Free: " + free / mb + "MB");
     System.out.println("Percent Used: " + ((double)used/(double)total)*100 + "%");
     System.out.println("Percent Free: " + ((double)free/(double)total)*100 + "%");
    }
    public static void log(Object message)
         {
            System.out.println(message);
         }

        public static int calcCPU(long cpuStartTime, long elapsedStartTime, int cpuCount)
        {
             long end = System.nanoTime();
             long totalAvailCPUTime = cpuCount * (end-elapsedStartTime);
             long totalUsedCPUTime = ManagementFactory.getThreadMXBean().getCurrentThreadCpuTime()-cpuStartTime;
             //log("Total CPU Time:" + totalUsedCPUTime + " ns.");
             //log("Total Avail CPU Time:" + totalAvailCPUTime + " ns.");
             float per = ((float)totalUsedCPUTime*100)/(float)totalAvailCPUTime;
             log( per);
             return (int)per;
        }

        static boolean isPrime(int n)
        {
     // 2 is the smallest prime
            if (n <= 2)
            {
                return n == 2;
            }
     // even numbers other than 2 are not prime
            if (n % 2 == 0)
            {
                return false;
            }
     // check odd divisors from 3
     // to the square root of n
         for (int i = 3, end = (int)Math.sqrt(n); i <= end; i += 2)
         {
            if (n % i == 0)
         {
         return false;
        }
        }
 return true;
}
    public static void main(String [] args)
    {
            int mb = 1024*1024;
            int gb = 1024*1024*1024;
             /* PHYSICAL MEMORY USAGE */
             System.out.println("\n**** Sizes in Mega Bytes ****\n");
            com.sun.management.OperatingSystemMXBean operatingSystemMXBean = (com.sun.management.OperatingSystemMXBean)ManagementFactory.getOperatingSystemMXBean();
            //RuntimeMXBean runtimeMXBean = ManagementFactory.getRuntimeMXBean();
            //operatingSystemMXBean = (com.sun.management.OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
            com.sun.management.OperatingSystemMXBean os = (com.sun.management.OperatingSystemMXBean)
            java.lang.management.ManagementFactory.getOperatingSystemMXBean();
            long physicalMemorySize = os.getTotalPhysicalMemorySize();
            System.out.println("PHYSICAL MEMORY DETAILS \n");
            System.out.println("total physical memory : " + physicalMemorySize / mb + "MB ");
            long physicalfreeMemorySize = os.getFreePhysicalMemorySize();
            System.out.println("total free physical memory : " + physicalfreeMemorySize / mb + "MB");
            /* DISC SPACE DETAILS */
            File diskPartition = new File("C:");
            File diskPartition1 = new File("D:");
            File diskPartition2 = new File("E:");
            long totalCapacity = diskPartition.getTotalSpace() / gb;
            long totalCapacity1 = diskPartition1.getTotalSpace() / gb;
            double freePartitionSpace = diskPartition.getFreeSpace() / gb;
            double freePartitionSpace1 = diskPartition1.getFreeSpace() / gb;
            double freePartitionSpace2 = diskPartition2.getFreeSpace() / gb;
            double usablePatitionSpace = diskPartition.getUsableSpace() / gb;
            System.out.println("\n**** Sizes in Giga Bytes ****\n");
            System.out.println("DISC SPACE DETAILS \n");
            //System.out.println("Total C partition size : " + totalCapacity + "GB");
            //System.out.println("Usable Space : " + usablePatitionSpace + "GB");
            System.out.println("Free Space in drive C: : " + freePartitionSpace + "GB");
            System.out.println("Free Space in drive D:  : " + freePartitionSpace1 + "GB");
            System.out.println("Free Space in drive E: " + freePartitionSpace2 + "GB");
            if(freePartitionSpace <= totalCapacity%10 || freePartitionSpace1 <= totalCapacity1%10)
            {
                System.out.println(" !!!alert!!!!");
            }
            else
                System.out.println("no alert");

            Runtime runtime;
            byte[] bytes;
            System.out.println("\n \n**MEMORY DETAILS  ** \n");
            // Print initial memory usage.
            runtime = Runtime.getRuntime();
            printUsage(runtime);

            // Allocate a 1 Megabyte and print memory usage
            bytes = new byte[1024*1024];
            printUsage(runtime);

            bytes = null;
            // Invoke garbage collector to reclaim the allocated memory.
            runtime.gc();

            // Wait 5 seconds to give garbage collector a chance to run
            try {
            Thread.sleep(5000);
            } catch(InterruptedException e) {
            e.printStackTrace();
            return;
            }

            // Total memory will probably be the same as the second printUsage call,
            // but the free memory should be about 1 Megabyte larger if garbage
            // collection kicked in.
            printUsage(runtime);
            for(int i = 0; i < 30; i++)
                     {
                         long start = System.nanoTime();
                        // log(start);
                        //number of available processors;
                         int cpuCount = ManagementFactory.getOperatingSystemMXBean().getAvailableProcessors();
                         Random random = new Random(start);
                         int seed = Math.abs(random.nextInt());
                         log("\n \n CPU USAGE DETAILS \n\n");
                         log("Starting Test with " + cpuCount + " CPUs and random number:" + seed);
                         int primes = 10000;
                         //
                         long startCPUTime = ManagementFactory.getThreadMXBean().getCurrentThreadCpuTime();
                         start = System.nanoTime();
                         while(primes != 0)
                         {
                            if(isPrime(seed))
                            {
                                primes--;
                            }
                            seed++;

                        }
                         float cpuPercent = calcCPU(startCPUTime, start, cpuCount);
                         log("CPU USAGE : " + cpuPercent + " % ");


                         try
                         {
                             Thread.sleep(1000);
                         }
                         catch (InterruptedException e) {}
        }

            try
            {
                Thread.sleep(500);
            }`enter code here`
            catch (Exception ignored) { }
        }
    }

The following code is Linux (maybe Unix) only, but it works in a real project.

    private double getAverageValueByLinux() throws InterruptedException {
    try {

        long delay = 50;
        List<Double> listValues = new ArrayList<Double>();
        for (int i = 0; i < 100; i++) {
            long cput1 = getCpuT();
            Thread.sleep(delay);
            long cput2 = getCpuT();
            double cpuproc = (1000d * (cput2 - cput1)) / (double) delay;
            listValues.add(cpuproc);
        }
        listValues.remove(0);
        listValues.remove(listValues.size() - 1);
        double sum = 0.0;
        for (Double double1 : listValues) {
            sum += double1;
        }
        return sum / listValues.size();
    } catch (Exception e) {
        e.printStackTrace();
        return 0;
    }

}

private long getCpuT throws FileNotFoundException, IOException {
    BufferedReader reader = new BufferedReader(new FileReader("/proc/stat"));
    String line = reader.readLine();
    Pattern pattern = Pattern.compile("\\D+(\\d+)\\D+(\\d+)\\D+(\\d+)\\D+(\\d+)")
    Matcher m = pattern.matcher(line);

    long cpuUser = 0;
    long cpuSystem = 0;
    if (m.find()) {
        cpuUser = Long.parseLong(m.group(1));
        cpuSystem = Long.parseLong(m.group(3));
    }
    return cpuUser + cpuSystem;
}

Make a batch file "Pc.bat" as, typeperf -sc 1 "\mukit\processor(_Total)\%% Processor Time"

You can use the class MProcess,

public MProcessor() {
    String s;
    try {
        Process ps = Runtime.getRuntime().exec("Pc.bat");
        BufferedReader br = new BufferedReader(new InputStreamReader(ps.getInputStream()));
        while((s = br.readLine()) != null) {
            System.out.println(s);
        }
    }
    catch( Exception ex ) {
        System.out.println(ex.toString());
    }
}

}

Then after some string manipulation, you get the CPU use. You can use the same process for other tasks.

--Mukit Hasan

    OperatingSystemMXBean osBean = ManagementFactory.getPlatformMXBean(OperatingSystemMXBean.class);
    System.out.println((osBean.getCpuLoad() * 100) + "%");

import com.sun.management.OperatingSystemMXBean

It only starts working after the second call so save the osBean and put it in a loop