How to Retrieve the PID of a Process Launched using ProcessBuilder in Java?

Retrieving the PID of a Process Launched from Java

When launching a process in Java using ProcessBuilder, you often need to obtain its process ID (PID) for further management or monitoring. Here's how you can achieve this:

In previous versions of Java, you could use Runtime.getRuntime().exec() to start a process and retrieve its PID using the ProcessHandle.pid() method. However, with the introduction of Java 9, ProcessBuilder offers a more refined approach.

<code class="java">import java.io.IOException;
import java.util.concurrent.ThreadLocalRandom;

public class GetProcessPID {

    public static void main(String[] args) {
        // Generate a random number for the process name
        String processName = "Process_" + ThreadLocalRandom.current().nextInt(1000);

        try {
            // Start the process with ProcessBuilder
            ProcessBuilder pb = new ProcessBuilder("cmd", "/c", processName);
            Process p = pb.start();

            // Retrieve and print the process PID
            long pid = p.pid();
            System.out.println("Process PID: " + pid);
        } catch (IOException e) {
            System.out.println("Error starting process: " + e.getMessage());
        }
    }
}</code>

This code demonstrates how to use ProcessBuilder to start a command prompt (cmd) window with a specified name (processName). The pid() method of the Process object is then used to obtain the PID of the newly created process, which is printed to the console.

Since Java 9, the pid() method is a straightforward way to retrieve the PID of processes launched using ProcessBuilder. It simplifies the process compared to using ProcessHandle in earlier Java versions.

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