Question

Im developing a simple console application using java. I want to display currently running jar files in my system. The following code is displaying all running process window.

try {


        String cmds[] = { "cmd", "/c", "tasklist" };
        Process myProcess = Runtime.getRuntime().exec(cmds);
        BufferedReader stdout = new BufferedReader(new InputStreamReader(
                myProcess.getInputStream()));
        String line = stdout.readLine();
        File file = new File("writer.txt");
        writer = new BufferedWriter(new FileWriter(file));
        while (line != null) {
            writer.write(line);
            writer.write("\n");
            System.out.println(line);
            line = stdout.readLine();
        }
        writer.close();


    } catch (Exception e) {// Catch exception if any
        System.err.println("Error: " + e.getMessage());
    }  

Im used

`String cmds[] = { "cmd", "/c", "jps" };`  

But its not displayed the process. Please anyone give the suggestions. Thanks n advance.

Answer 1

The only thing you actually can see are running java virtual machines but the operating system can’t see what threads are running inside the jvms.

A ‘jar’ file is not an executable file. It is nothing but a java library with an extra entry in the libraries manifest, that names one class with a ‘main’ methods. So if you start java with the jar option and pass such a jar, the virtual machine will use this method to start the main thread.

But we still can have several additional threads running in the same virtual machine and each thread could fit in the concept of an application.

For jps :

If jps is run without specifying a hostid, it will look for instrumented JVMs on the local host.

and

This utility is unsupported and may not be available in future versions of the JDK. It is not currently available on Windows 98 and Windows ME platforms.

So if the virtual machine is not instrumented, then jps will not report anything (and I doubt that it can list the jar files that are on the classpaths or that have been used to load classes so far).