Shutting down a computer

Create your own function to execute an OS command through the command line?

For the sake of an example. But know where and why you'd want to use this as others note.

public static void main(String arg[]) throws IOException{
    Runtime runtime = Runtime.getRuntime();
    Process proc = runtime.exec("shutdown -s -t 0");
    System.exit(0);
}

Here's another example that could work cross-platform:

public static void shutdown() throws RuntimeException, IOException {
    String shutdownCommand;
    String operatingSystem = System.getProperty("os.name");

    if ("Linux".equals(operatingSystem) || "Mac OS X".equals(operatingSystem)) {
        shutdownCommand = "shutdown -h now";
    }
    // This will work on any version of windows including version 11 
    else if (operatingSystem.contains("Windows")) {
        shutdownCommand = "shutdown.exe -s -t 0";
    }
    else {
        throw new RuntimeException("Unsupported operating system.");
    }

    Runtime.getRuntime().exec(shutdownCommand);
    System.exit(0);
}

The specific shutdown commands may require different paths or administrative privileges.