How do I get the Java classpath?

By Wayan in Core API, Management 0 Comment

The RuntimeMXBean.getClassPath() returns the Java class path that is used by the system class loader to search for class files. This method is equivalent to System.getProperty("java.class.path").

Multiple paths in the Java class path are separated by the path separator character of the platform of the Java virtual machine being monitored.

package org.kodejava.lang.management;

import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;

public class GetClassPath {
    public static void main(String[] args) {
        RuntimeMXBean bean = ManagementFactory.getRuntimeMXBean();
        String classPath = bean.getClassPath();
        System.out.println("ClassPath = " + classPath);
    }
}

How do I get system properties information?

By Wayan in Core API, Management 0 Comment 
package org.kodejava.lang.management;

import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.util.Map;
import java.util.Set;

public class GetSystemProperties {
    public static void main(String[] args) {
        RuntimeMXBean bean = ManagementFactory.getRuntimeMXBean();

        // Returns a map of names and values of all system
        // properties. This method calls System.getProperties()
        // to get all system properties. Properties whose
        // name or value is not a String are omitted.
        Map<String, String> systemProperties = bean.getSystemProperties();
        Set<String> keys = systemProperties.keySet();
        for (String key : keys) {
            String value = systemProperties.get(key);
            System.out.printf("Property[%s] = %s%n", key, value);
        }
    }
}

Some properties produced by the code snippet above are:

Property[java.specification.version] = 17
Property[sun.cpu.isalist] = amd64
Property[sun.jnu.encoding] = Cp1252
Property[java.vm.vendor] = Oracle Corporation
Property[sun.arch.data.model] = 64
Property[user.variant] = 
Property[java.vendor.url] = https://java.oracle.com/
...
...
Property[java.vm.info] = mixed mode, sharing.
Property[java.vendor] = Oracle Corporation.
Property[java.vm.version] = 17+35-LTS-2724.
Property[sun.io.unicode.encoding] = UnicodeLittle.
Property[java.class.version] = 61.0.

How do I get the start time of a JVM?

By Wayan in Core API, Management 0 Comment 
package org.kodejava.lang.management;

import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.util.Date;

public class GetStartTime {
    public static void main(String[] args) {
        RuntimeMXBean bean = ManagementFactory.getRuntimeMXBean();

        // Returns the start time of the Java virtual machine in 
        // milliseconds. This method returns the approximate time 
        // when the Java virtual machine started.
        long startTime = bean.getStartTime();
        Date startDate = new Date(startTime);
        System.out.println("Start Time = " + startTime);
        System.out.println("Start Date = " + startDate);
    }
}

The result of the code snippet above:

Start Time = 1634391703196
Start Date = Sat Oct 16 21:41:43 CST 2021

How do I get the uptime of a JVM?

By Wayan in Core API, Management 0 Comment

The following code snippet demonstrates how to get the time for how long has the JVM been running.

package org.kodejava.lang.management;

import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;

public class GetUptime {
    public static void main(String[] args) {
        RuntimeMXBean bean = ManagementFactory.getRuntimeMXBean();

        // Returns the uptime of the Java virtual machine in
        // milliseconds.
        long uptime = bean.getUptime();
        System.out.printf("Uptime = %d (ms).", uptime);
    }
}

The output of the code snippet above:

Uptime = 125 (ms).

How do I get process ID of a Java application?

By Wayan in Core API, Management 3 Comments

The code below show you how to get the process ID of a Java application. We can use the ManagementFactory.getRuntimeMXBean().getName() to get the process ID. In Windows the method return a string in the form of [PID]@[MACHINE_NAME].

Since JDK 10, we can use ManagementFactory.getRuntimeMXBean().getPid() method to get the process ID. This method returns the process ID representing the running Java virtual machine.

package org.kodejava.lang.management;

import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;

public class GetProcessID {
    public static void main(String[] args) {
        RuntimeMXBean bean = ManagementFactory.getRuntimeMXBean();

        // Get name representing the running Java virtual machine.
        // It returns something like 35656@Krakatau. The value before
        // the @ symbol is the PID.
        String jvmName = bean.getName();
        System.out.println("Name = " + jvmName);

        // Extract the PID by splitting the string returned by the
        // bean.getName() method.
        long pid = Long.parseLong(jvmName.split("@")[0]);
        System.out.println("PID  = " + pid);

        // Get the process ID representing the running Java virtual machine.
        // Since JDK 10.
        pid = ManagementFactory.getRuntimeMXBean().getPid();
        System.out.println("PID = " + pid);

    }
}

Here is the result of the code above:

Name = 35656@Krakatau
PID  = 35656
PID  = 35656