FULL PRODUCT VERSION :
java version "9-ea"
Java(TM) SE Runtime Environment (build 9-ea+155)
Java HotSpot(TM) 64-Bit Server VM (build 9-ea+155, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
The ProcessHandle.Info the arguments() method always return a non present optional. The reason for this is that the implementation in the ProcessHandleImpl.Info does not ever change the value of the private field arguments. It is set null in the constructor and it is only used in other places but never set.

For this reason the commandLine() method is always not present Optional, as it is present only if the command is not null and there are arguments.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Just call ProcessHandle.Info.arguments() on any ProcessHandle.Info instance.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I expect the implementation class implementing the feature.
ACTUAL -
"C:\Program Files\Java\jdk-9\bin\java" "-javaagent:C:\Program Files (x86)\JetBrains\IntelliJ IDEA Community Edition 171.3019.7\lib\idea_rt.jar=53069:C:\Program Files (x86)\JetBrains\IntelliJ IDEA Community Edition 171.3019.7\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\Peter_Verhas\Dropbox\java_9-Mastering\sources\chapter09\build\classes\main packt.mastering.java9.process.DumpThisProcess
Command: C:\Program Files\Java\jdk-9\bin\java.exe
Command Line: not present
Arguments:
Number of arguments: 0
CPU: PT0.3432022S
Start time: 2017-03-09T13:26:52.097Z
User: BUDAPEST\Peter_Verhas
Pid: 7636
Children
Descendants
toString [user: Optional[BUDAPEST\Peter_Verhas], cmd: C:\Program Files\Java\jdk-9\bin\java.exe, startTime: Optional[2017-03-09T13:26:52.097Z], totalTime: Optional[PT0.4368028S]]

Process finished with exit code 0


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package packt.mastering.java9.process;

import java.lang.ProcessHandle.Info;
import java.time.Duration;
import java.time.Instant;

import static packt.mastering.java9.process.DemoOutput.out;

public class DumpThisProcess {
    public static void main(String[] args) {
        ProcessHandle me = ProcessHandle.current();
        Info info = me.info();
        out("Command: {0}", info.command().orElse("??"));
        out("Command Line: {0}", info.commandLine().orElse("not present"));
        out("Arguments: {0}", String.join(" ", info.arguments().orElse(new String[0])));
        out("Number of arguments: {0}", info.arguments().orElse(new String[0]).length);
        out("CPU: {0}", info.totalCpuDuration().orElse(Duration.ZERO));
        out("Start time: {0}", info.startInstant().orElse(Instant.EPOCH));
        out("User: {0}", info.user().orElse("??"));
        out("Pid: {0,number,#}", me.getPid());
        out("Children","");
        me.children().forEach( child -> out("child pid:",child.getPid()));
        out("Descendants","");
        me.descendants().forEach( descendant -> out("descendant pid:",descendant.getPid()));
        out("toString {0}",me.info().toString());
    }
}
---------- END SOURCE ----------