How do I read system information in Java? [duplicate] - java

I'm currently building a Java app that could end up being run on many different platforms, but primarily variants of Solaris, Linux and Windows.
Has anyone been able to successfully extract information such as the current disk space used, CPU utilisation and memory used in the underlying OS? What about just what the Java app itself is consuming?
Preferrably I'd like to get this information without using JNI.


You can get some limited memory information from the Runtime class. It really isn't exactly what you are looking for, but I thought I would provide it for the sake of completeness. Here is a small example. Edit: You can also get disk usage information from the java.io.File class. The disk space usage stuff requires Java 1.6 or higher.
public class Main {
public static void main(String[] args) {
/* Total number of processors or cores available to the JVM */
System.out.println("Available processors (cores): " +
Runtime.getRuntime().availableProcessors());
/* Total amount of free memory available to the JVM */
System.out.println("Free memory (bytes): " +
Runtime.getRuntime().freeMemory());
/* This will return Long.MAX_VALUE if there is no preset limit */
long maxMemory = Runtime.getRuntime().maxMemory();
/* Maximum amount of memory the JVM will attempt to use */
System.out.println("Maximum memory (bytes): " +
(maxMemory == Long.MAX_VALUE ? "no limit" : maxMemory));
/* Total memory currently available to the JVM */
System.out.println("Total memory available to JVM (bytes): " +
Runtime.getRuntime().totalMemory());
/* Get a list of all filesystem roots on this system */
File[] roots = File.listRoots();
/* For each filesystem root, print some info */
for (File root : roots) {
System.out.println("File system root: " + root.getAbsolutePath());
System.out.println("Total space (bytes): " + root.getTotalSpace());
System.out.println("Free space (bytes): " + root.getFreeSpace());
System.out.println("Usable space (bytes): " + root.getUsableSpace());
}
}
}


The java.lang.management package does give you a whole lot more info than Runtime - for example it will give you heap memory (ManagementFactory.getMemoryMXBean().getHeapMemoryUsage()) separate from non-heap memory (ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage()).
You can also get process CPU usage (without writing your own JNI code), but you need to cast the java.lang.management.OperatingSystemMXBean to a com.sun.management.OperatingSystemMXBean. This works on Windows and Linux, I haven't tested it elsewhere.
For example ... call the get getCpuUsage() method more frequently to get more accurate readings.
public class PerformanceMonitor {
private int availableProcessors = getOperatingSystemMXBean().getAvailableProcessors();
private long lastSystemTime = 0;
private long lastProcessCpuTime = 0;
public synchronized double getCpuUsage()
{
if ( lastSystemTime == 0 )
{
baselineCounters();
return;
}
long systemTime = System.nanoTime();
long processCpuTime = 0;
if ( getOperatingSystemMXBean() instanceof OperatingSystemMXBean )
{
processCpuTime = ( (OperatingSystemMXBean) getOperatingSystemMXBean() ).getProcessCpuTime();
}
double cpuUsage = (double) ( processCpuTime - lastProcessCpuTime ) / ( systemTime - lastSystemTime );
lastSystemTime = systemTime;
lastProcessCpuTime = processCpuTime;
return cpuUsage / availableProcessors;
}
private void baselineCounters()
{
lastSystemTime = System.nanoTime();
if ( getOperatingSystemMXBean() instanceof OperatingSystemMXBean )
{
lastProcessCpuTime = ( (OperatingSystemMXBean) getOperatingSystemMXBean() ).getProcessCpuTime();
}
}
}


I think the best method out there is to implement the SIGAR API by Hyperic. It works for most of the major operating systems ( darn near anything modern ) and is very easy to work with. The developer(s) are very responsive on their forum and mailing lists. I also like that it is GPL2 Apache licensed. They provide a ton of examples in Java too!
SIGAR == System Information, Gathering And Reporting tool.


There's a Java project that uses JNA (so no native libraries to install) and is in active development. It currently supports Linux, OSX, Windows, Solaris and FreeBSD and provides RAM, CPU, Battery and file system information.
https://github.com/oshi/oshi


For windows I went this way.
com.sun.management.OperatingSystemMXBean os = (com.sun.management.OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
long physicalMemorySize = os.getTotalPhysicalMemorySize();
long freePhysicalMemory = os.getFreePhysicalMemorySize();
long freeSwapSize = os.getFreeSwapSpaceSize();
long commitedVirtualMemorySize = os.getCommittedVirtualMemorySize();
Here is the link with details.


You can get some system-level information by using System.getenv(), passing the relevant environment variable name as a parameter. For example, on Windows:
System.getenv("PROCESSOR_IDENTIFIER")
System.getenv("PROCESSOR_ARCHITECTURE")
System.getenv("PROCESSOR_ARCHITEW6432")
System.getenv("NUMBER_OF_PROCESSORS")
For other operating systems the presence/absence and names of the relevant environment variables will differ.


Add OSHI dependency via maven:
<dependency>
<groupId>com.github.dblock</groupId>
<artifactId>oshi-core</artifactId>
<version>2.2</version>
</dependency>
Get a battery capacity left in percentage:
SystemInfo si = new SystemInfo();
HardwareAbstractionLayer hal = si.getHardware();
for (PowerSource pSource : hal.getPowerSources()) {
System.out.println(String.format("%n %s # %.1f%%", pSource.getName(), pSource.getRemainingCapacity() * 100d));
}


Have a look at the APIs available in the java.lang.management package. For example:
OperatingSystemMXBean.getSystemLoadAverage()
ThreadMXBean.getCurrentThreadCpuTime()
ThreadMXBean.getCurrentThreadUserTime()
There are loads of other useful things in there as well.


Usually, to get low level OS information you can call OS specific commands which give you the information you want with Runtime.exec() or read files such as /proc/* in Linux.


CPU usage isn't straightforward -- java.lang.management via com.sun.management.OperatingSystemMXBean.getProcessCpuTime comes close (see Patrick's excellent code snippet above) but note that it only gives access to time the CPU spent in your process. it won't tell you about CPU time spent in other processes, or even CPU time spent doing system activities related to your process.
for instance i have a network-intensive java process -- it's the only thing running and the CPU is at 99% but only 55% of that is reported as "processor CPU".
don't even get me started on "load average" as it's next to useless, despite being the only cpu-related item on the MX bean. if only sun in their occasional wisdom exposed something like "getTotalCpuTime"...
for serious CPU monitoring SIGAR mentioned by Matt seems the best bet.


On Windows, you can run the systeminfo command and retrieves its output for instance with the following code:
private static class WindowsSystemInformation
{
static String get() throws IOException
{
Runtime runtime = Runtime.getRuntime();
Process process = runtime.exec("systeminfo");
BufferedReader systemInformationReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
StringBuilder stringBuilder = new StringBuilder();
String line;
while ((line = systemInformationReader.readLine()) != null)
{
stringBuilder.append(line);
stringBuilder.append(System.lineSeparator());
}
return stringBuilder.toString().trim();
}
}


If you are using Jrockit VM then here is an other way of getting VM CPU usage. Runtime bean can also give you CPU load per processor. I have used this only on Red Hat Linux to observer Tomcat performance. You have to enable JMX remote in catalina.sh for this to work.
JMXServiceURL url = new JMXServiceURL("service:jmx:rmi:///jndi/rmi://my.tomcat.host:8080/jmxrmi");
JMXConnector jmxc = JMXConnectorFactory.connect(url, null);
MBeanServerConnection conn = jmxc.getMBeanServerConnection();
ObjectName name = new ObjectName("oracle.jrockit.management:type=Runtime");
Double jvmCpuLoad =(Double)conn.getAttribute(name, "VMGeneratedCPULoad");


It is still under development but you can already use jHardware
It is a simple library that scraps system data using Java. It works in both Linux and Windows.
ProcessorInfo info = HardwareInfo.getProcessorInfo();
//Get named info
System.out.println("Cache size: " + info.getCacheSize());
System.out.println("Family: " + info.getFamily());
System.out.println("Speed (Mhz): " + info.getMhz());
//[...]


One simple way which can be used to get the OS level information and I tested in my Mac which works well :
OperatingSystemMXBean osBean =
(OperatingSystemMXBean)ManagementFactory.getOperatingSystemMXBean();
return osBean.getProcessCpuLoad();
You can find many relevant metrics of the operating system here


To get the System Load average of 1 minute, 5 minutes and 15 minutes inside the java code, you can do this by executing the command cat /proc/loadavg using and interpreting it as below:
Runtime runtime = Runtime.getRuntime();
BufferedReader br = new BufferedReader(
new InputStreamReader(runtime.exec("cat /proc/loadavg").getInputStream()));
String avgLine = br.readLine();
System.out.println(avgLine);
List<String> avgLineList = Arrays.asList(avgLine.split("\\s+"));
System.out.println(avgLineList);
System.out.println("Average load 1 minute : " + avgLineList.get(0));
System.out.println("Average load 5 minutes : " + avgLineList.get(1));
System.out.println("Average load 15 minutes : " + avgLineList.get(2));
And to get the physical system memory by executing the command free -m and then interpreting it as below:
Runtime runtime = Runtime.getRuntime();
BufferedReader br = new BufferedReader(
new InputStreamReader(runtime.exec("free -m").getInputStream()));
String line;
String memLine = "";
int index = 0;
while ((line = br.readLine()) != null) {
if (index == 1) {
memLine = line;
}
index++;
}
// total used free shared buff/cache available
// Mem: 15933 3153 9683 310 3097 12148
// Swap: 3814 0 3814
List<String> memInfoList = Arrays.asList(memLine.split("\\s+"));
int totalSystemMemory = Integer.parseInt(memInfoList.get(1));
int totalSystemUsedMemory = Integer.parseInt(memInfoList.get(2));
int totalSystemFreeMemory = Integer.parseInt(memInfoList.get(3));
System.out.println("Total system memory in mb: " + totalSystemMemory);
System.out.println("Total system used memory in mb: " + totalSystemUsedMemory);
System.out.println("Total system free memory in mb: " + totalSystemFreeMemory);


Hey you can do this with java/com integration. By accessing WMI features you can get all the information.


Not exactly what you asked for, but I'd recommend checking out ArchUtils and SystemUtils from commons-lang3. These also contain some relevant helper facilities, e.g.:
import static org.apache.commons.lang3.ArchUtils.*;
import static org.apache.commons.lang3.SystemUtils.*;
System.out.printf("OS architecture: %s\n", OS_ARCH); // OS architecture: amd64
System.out.printf("OS name: %s\n", OS_NAME); // OS name: Linux
System.out.printf("OS version: %s\n", OS_VERSION); // OS version: 5.18.16-200.fc36.x86_64
System.out.printf("Is Linux? - %b\n", IS_OS_LINUX); // Is Linux? - true
System.out.printf("Is Mac? - %b\n", IS_OS_MAC); // Is Mac? - false
System.out.printf("Is Windows? - %b\n", IS_OS_WINDOWS); // Is Windows? - false
System.out.printf("JVM name: %s\n", JAVA_VM_NAME); // JVM name: Java HotSpot(TM) 64-Bit Server VM
System.out.printf("JVM vendor: %s\n", JAVA_VM_VENDOR); // JVM vendor: Oracle Corporation
System.out.printf("JVM version: %s\n", JAVA_VM_VERSION); // JVM version: 11.0.12+8-LTS-237
System.out.printf("Username: %s\n", getUserName()); // Username: johndoe
System.out.printf("Hostname: %s\n", getHostName()); // Hostname: garage-pc
var processor = getProcessor();
System.out.printf("CPU arch: %s\n", processor.getArch()) // CPU arch: BIT_64
System.out.printf("CPU type: %s\n", processor.getType()); // CPU type: X86

Related

Detect CPU model information

Is there a way to get info about cpu model (for unix system) in Java? I mean without using system commands like cat /proc/cpuinfo.
I want get something like: "Intel(R) Xeon(R) CPU E5-2640 0 # 2.50GHz"
Thanks!

I think this question is a duplicata for this one get OS-level system information, however I'll re-post the best answer for that one.
You can get some limited memory information from the Runtime class. It
really isn't exactly what you are looking for, but I thought I would
provide it for the sake of completeness. Here is a small example. You
can also get disk usage information from the java.io.File class. The
disk space usage stuff requires Java 1.6 or higher.
public class Main {
public static void main(String[] args) {
/* Total number of processors or cores available to the JVM */
System.out.println("Available processors (cores): " +
Runtime.getRuntime().availableProcessors());
/* Total amount of free memory available to the JVM */
System.out.println("Free memory (bytes): " +
Runtime.getRuntime().freeMemory());
/* This will return Long.MAX_VALUE if there is no preset limit */
long maxMemory = Runtime.getRuntime().maxMemory();
/* Maximum amount of memory the JVM will attempt to use */
System.out.println("Maximum memory (bytes): " +
(maxMemory == Long.MAX_VALUE ? "no limit" : maxMemory));
/* Total memory currently available to the JVM */
System.out.println("Total memory available to JVM (bytes): " +
Runtime.getRuntime().totalMemory());
/* Get a list of all filesystem roots on this system */
File[] roots = File.listRoots();
/* For each filesystem root, print some info */
for (File root : roots) {
System.out.println("File system root: " + root.getAbsolutePath());
System.out.println("Total space (bytes): " + root.getTotalSpace());
System.out.println("Free space (bytes): " + root.getFreeSpace());
System.out.println("Usable space (bytes): " + root.getUsableSpace());
}
}
}
In your case you want the Runtime.getRuntime().availableProcessors().
There is another way, using sigar API. For that you need to download sigar from this link, and check this to include it in your project How to include SIGAR API in Java Project.
You will then use something like this:
import org.hyperic.sigar.Sigar;
import org.hyperic.sigar.SigarException;
public class CpuInfo {
public static void main(String[] args) throws SigarException {
Sigar sigar = new Sigar();
org.hyperic.sigar.CpuInfo[] cpuInfoList = sigar.getCpuInfoList();
for(org.hyperic.sigar.CpuInfo info : cpuInfoList){
System.out.println("CPU Model : " + info.getModel());
}
}
}

If you want that level of detail, your best bet is to read the contents of /proc/cpuinfo and parse out the part you want.
Otherwise, from within a JVM, you can get a count of the number of processor cores
int count = Runtime.getRuntime().availableProcessors();
or OS architecture:
String arch = System.getProperty("os.arch");

I would simply read /proc/cpuinfo.
String model = Files.lines(Paths.get("/proc/cpuinfo"))
.filter(line -> line.startsWith("model name"))
.map(line -> line.replaceAll(".*: ", ""))
.findFirst().orElse("")

It seems Sigar mentioned in another answer is no longer maintained and does not work with recent Windows versions because of 64b/32b incompatibilites (see PR 142).
There seems to be another library for the purposes, which seems to be alive (last version published a few days ago) OSHI.
With OSHI you can get the information like this:
SystemInfo si = new SystemInfo();
HardwareAbstractionLayer hal = si.getHardware();
CentralProcessor cpu = hal.getProcessor();
String name = cpu.getProcessorIdentifier().getName();

Get OS Information Correctly in Java or C#

I want to get OS name with edition using java or C# as mentioned in below example :
Example : Microsoft Windows 8.1 Enterprise
I have tried below :
In java tried System.getProperty("os.name")
=> It does not provide OS edition
One ways is to get OS name from registry
Getting "ProductName" from \HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion
I also tried SYSTEMINFO command, it provides OS Name. but since it shows output different language. its not possible to check variable name from output.
But I want to find a way other than finding from registry, so that even if in future versions of OS, registry path changes, App should provide correct OS name.
Is there any other reliable way to find OS name with edition ?

Have a look at the apache commons lang library - OS_ARCH, OS_NAME, OS_VERSION
maybe it retrieves what you need. Below is a link to its javadocs:
https://commons.apache.org/proper/commons-lang/javadocs/api-2.4/org/apache/commons/lang/SystemUtils.html

Finally I used below code because I analysed that most probably registry path will not be changed.
private final String STR_OS_NAME_REGISTRY_QUERY = "reg query \"HKLM\\Software\\Microsoft\\Windows NT\\CurrentVersion\" /v \"ProductName\"";
// Get OS name
objProcessName = Runtime.getRuntime().exec(STR_OS_NAME_REGISTRY_QUERY);
objProcessName.waitFor();
objBufferReader = new BufferedReader(new InputStreamReader(objProcessName.getInputStream()));
lstJavaInfo = new ArrayList<>();
while ((sLine = objBufferReader.readLine()) != null)
{
lstJavaInfo.add(sLine);
}
objProcessName.waitFor();
if(lstJavaInfo.size() < 3)
{
return "-";
}
String[] sarr = lstJavaInfo.get(2).split("\\s+");
for(int nIndex = 3 ; nIndex < sarr.length ; nIndex++)
{
sOSArchitecture = sOSArchitecture + sarr[nIndex] + " ";
}

How can I calclulate the diskspace of a remote machine using java?

Can anyone suggest me how can I modify the below code which is currently calculating the free disk space(C:) of my local system(Windows OS) to calculate the free disk space (C:) of the remote machine(Windows OS) using java?
import java.io.File;
public class DiskMemory
{
public static void main(String[] args)
{
File file = new File("C:");
//total disk space in bytes.
long totalSpace = file.getTotalSpace();
//unallocated free disk space in bytes.
long usableSpace = file.getUsableSpace();
//unallocated free disk space available to current user.
long freeSpace = file.getFreeSpace();
System.out.println(" ==Total Memory Allocation == ");
System.out.println("Total size : " + totalSpace + " bytes");
System.out.println("Space free : " + usableSpace + " bytes");
System.out.println("Space free : " + freeSpace + " bytes");
System.out.println(" === mega bytes ===");
System.out.println("Total size : " + totalSpace /1024 /1024 + " mb");
System.out.println("Space free : " + usableSpace /1024 /1024 + " mb");
System.out.println("Space free : " + freeSpace /1024 /1024 + " mb");
}
}

After looking at Apache's VFS, I found it overly complicated to get disk space usage, and it relies on jCIFS ( https://jcifs.samba.org/ ), which will do it with less hassel.
SmbFile file = new SmbFile("smb://[user]:[pass]#[server]/[share]");
System.out.println(file.getDiskFreeSpace()); // Space free on share
System.out.println(file.length()); // Total space available on share

You could look into using commons VFS for accessing the remote file systems and determining the file size
http://commons.apache.org/proper/commons-vfs/
This would allow you to get a file representing the remote directory (FileObject in VFS lingo) and get the size much in the same way you are doing already. Have a look at the website for an example. You could use VFS to query your local disk space as well.

Since you have access to all the machines whose disk space you want to calculate, you can write a simple client server program to solve the problem.
The high level overview of the system will be the following :
Let C be your machine, let s1, s2, s3, ..., sN be the N machines whose disk space you want on C.
On each the s machines, (s1, s2, etc), you need to run a server which is listening on some port (choose a port > 1024).
On machine C, there should be a client which will connect to all the s machines to get the usage.
Look up client server programming in java, it's pretty straightforward.

ChannelInputStream skip method is very slow

I have following piece of test code:
try {
InputStream is;
Stopwatch.start("FileInputStream");
is = new FileInputStream(imageFile.toFile());
is.skip(1024*1024*1024);
is.close();
Stopwatch.stop();
Stopwatch.start("Files.newInputStream");
is = Files.newInputStream(imageFile);
is.skip(1024*1024*1024);
is.close();
Stopwatch.stop();
}
catch(Exception e)
{
}
and I have following output:
Start: FileInputStream
FileInputStream : 0 ms
Start: Files.newInputStream
Files.newInputStream : 3469 ms
Do you have any idea what is going on? Why skip is so slow in the second case?
I need to use InputStreams acquired from channels because my test have shown that best for my task is to have two threads reading from file simultaneously (and I can notice any improvement only when I am using Streams from Channels).
During tests I figured out that I can do something like this:
SeekableByteChannel sbc = Files.newByteChannel(imageFile);
sbc.position(1024*1024*1024);
is = Channels.newInputStream(sbc);
which takes only avg. 28ms but that does not help me a lot because to use that I would have to make major API changes.
My platform:
Linux galileo 3.11.0-13-generic #20-Ubuntu SMP Wed Oct 23 07:38:26 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
java version "1.7.0_45"
Java(TM) SE Runtime Environment (build 1.7.0_45-b18)
Java HotSpot(TM) 64-Bit Server VM (build 24.45-b08, mixed mode)

Looking at the source, it appears that the default implementation of skip() is actually reading through (and discarding) the stream content until it reaches the target position:
public long skip(long n) throws IOException {
long remaining = n;
int nr;
if (n <= 0) {
return 0;
}
int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
byte[] skipBuffer = new byte[size];
while (remaining > 0) {
nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
if (nr < 0) {
break;
}
remaining -= nr;
}
return n - remaining;
}
The SeekableByteChannel#position() method probably just updates an offset pointer, which doesn't actually require any I/O. Presumably, FileInputStream overrides the skip() method with a similar optimization. The documentation supports this theory:
This method may skip more bytes than are remaining in the backing file. This produces no exception and the number of bytes skipped may include some number of bytes that were beyond the EOF of the backing file. Attempting to read from the stream after skipping past the end will result in -1 indicating the end of the file.
On platter disks or network storage, this could have a significant impact.

Try to set the range with GetObjectRequest.setRange to have the same behavior of skip.
GetObjectRequest req = new GetObjectRequest(BUCKET_NAME, "myfile.zip");
req.setRange(1024); // start download skiping 1024 bytes
S3ObjectInputStream in = client.getObject(req).getObjectContent();
// read "in" while not eof
I used this to avoid SocketTimeoutException on my implementation.
Each time I got a SocketTimeoutException I restart the download using the setRange to skip the bytes that I already downloaded.

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

I would like to monitor the following system information in Java:
Current CPU usage** (percent)
Available memory* (free/total)
Available disk space (free/total)
*Note that I mean overall memory available to the whole system, not just the JVM.
I'm looking for a cross-platform solution (Linux, Mac, and Windows) that doesn't rely on my own code calling external programs or using JNI. Although these are viable options, I would prefer not to maintain OS-specific code myself if someone already has a better solution.
If there's a free library out there that does this in a reliable, cross-platform manner, that would be great (even if it makes external calls or uses native code itself).
Any suggestions are much appreciated.
To clarify, I would like to get the current CPU usage for the whole system, not just the Java process(es).
The SIGAR API provides all the functionality I'm looking for in one package, so it's the best answer to my question so far. However, due it being licensed under the GPL, I cannot use it for my original purpose (a closed source, commercial product). It's possible that Hyperic may license SIGAR for commercial use, but I haven't looked into it. For my GPL projects, I will definitely consider SIGAR in the future.
For my current needs, I'm leaning towards the following:
For CPU usage, OperatingSystemMXBean.getSystemLoadAverage() / OperatingSystemMXBean.getAvailableProcessors() (load average per cpu)
For memory, OperatingSystemMXBean.getTotalPhysicalMemorySize() and OperatingSystemMXBean.getFreePhysicalMemorySize()
For disk space, File.getTotalSpace() and File.getUsableSpace()
Limitations:
The getSystemLoadAverage() and disk space querying methods are only available under Java 6. Also, some JMX functionality may not be available to all platforms (i.e. it's been reported that getSystemLoadAverage() returns -1 on Windows).
Although originally licensed under GPL, it has been changed to Apache 2.0, which can generally be used for closed source, commercial products.

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,
/*
*Md. Mukit Hasan
*CSE-JU,35
**/
import java.io.*;
public class MProcessor {
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

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