Develop Reference

How to disable 'headless java mode' to be able to run .jre GUI application using command line on Ubuntu

I have problem with running my java GUI program using cmd on Ubuntu Linux. When I run it using IntelliJ it works just fine, but using cmd breaks it.
From my research I have understood that the problem might be caused by me downloading the 'headless java version'.
So I d like to ask how can I solve this problem. How to mby reinstall it correctly or something that would help.
Thx a lot
I tried:
java -jar TIcTacToe.jar
But, outcome is:
Exception in thread "main" java.awt.HeadlessException:
No X11 DISPLAY variable was set,
or no headful library support was found,
but this program performed an operation which requires it,
at java.desktop/java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:166)
at java.desktop/java.awt.Window.<init>(Window.java:553)
at java.desktop/java.awt.Frame.<init>(Frame.java:428)
at java.desktop/java.awt.Frame.<init>(Frame.java:393)
at java.desktop/javax.swing.JFrame.<init>(JFrame.java:180)
at TicTacToe.<init>(TicTacToe.java:7)
at Main.main(Main.java:3)
I am expecting to be able to run my .jre file using cmd.

Why is the jar file immediately terminated after being called using a Python script?

I'm currently programming a Python script that opens a file in an different directory that the user enters in an input box. Everything runs fine but the jar file I used for testing doesn't run or show up. I'm using the Shimeji-ee.jar in testing, and at one point its tray icon showed up but disappeared immediately.
I tried running it in command prompt(since calling the jar file using the script is similar to running a file in CMD) and discovered that it only runs as long as the CMD window is open. A few searches later, I've found a way to run files in CMD that keeps it running even after closing the CMD. I wrote it in my script, no errors, but the Shimeji nor its tray icon doesn't ever appear anymore.
I've added a line at the end of my script that is also told to be an efficient way of keeping the script running, but it doesn't work either(could be another mistake here):
while True:
keyboard.wait('q')
if keyboard.is_pressed:
sys.exit()
Here's the line of code in my script that does the calling:
subprocess.run(['D:', 'cd', PurePath(fileDirectory), 'START', '""', fileToExecute], cwd=os.getcwd(), shell=True)
The code I learnt that makes a file run in the background(similar to adding & in a Linux terminal):
START "" program
I've had thoughts that the jar file I'm using could be the problem, but I haven't found any answers for hours. Is there anything wrong with the code or am I missing something?
Update:
Code finally worked after the first answer but I received an error that seemed it read the file as a double forward slash like this:
# The network path was not found //
or
# The system could not find the file //
The solution I found was just removing the '""' part of the code, which makes the code look like this:
subprocess.run(['START', fileToExecute], cwd=PurePath(fileDirectory), shell=True)

The problem is that your code:
subprocess.run(['D:', 'cd', PurePath(fileDirectory), 'START', '""', fileToExecute], cwd=os.getcwd(), shell=True)
executes the command D: with the arguments cd somedirectory START "" fileToExecute, which changes the current drive of the shell to the D drive and then terminates.
You probably want to execute
subprocess.run(['START', '""', fileToExecute], cwd=PurePath(fileDirectory), shell=True)

Trying to rename a computer OR execute a .bat file in Java

I'm trying to write a script to rename a computer (among other things) but just can't seem to figure it out. I don't really care what method I use to change the computer as long as i can change it. I found out how to read the computer name by doing
String computername = InetAddress.getLocalHost().getHostName();
However, that doesn't seem to offer any help in setting the computer name. Is there a way to set the Computer Name directly in the java console?
If not, or if anyone has better experience in this area, I also wrote a script using powershell 2.0 that renames the computer. I'm trying to figure out how to run that using
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec("file location");
I followed the guide here but when trying to run a test .bat file that should just open the command line I just get this output in the java console:
C:\Users\Stephen\Desktop\opencmd.bat is found
OUTPUT>
OUTPUT>C:\Users\Stephen\workspace\UNM computer rename>cmd.exe
OUTPUT>Microsoft Windows [Version 6.1.7601]
OUTPUT>Copyright (c) 2009 Microsoft Corporation. All rights reserved.
OUTPUT>
It looks like it's just spitting back the command line output into the java console, instead of just running the command and opening the cmd line.
I would really appreciate input as I'm in a crunch for time here, thanks!

First, JDK really does not provide pure java API that allows changing computer name. So you have to run script.
Second, if you want to run script using Runtime you have to provide correct command line. So first try to run your script manually. I believe it accepts a least one parameter (the new computer name). So run it from command prompt and see it is working. Then put it to the working directory of your java program and copy/paste the command line into the java code and see that it is working now. if you want you can read STDOUT of your script and/or get its return code. If you do not care about its output just call process.waitFor() and then get the return code.
Be careful with arguments. Windows computer name may contain unicode characters and spaces. If it contains spaces surround it with quotes. Concerning unicode just try. I hope it will not cause problems to you.
You can also use ProcessBuilder class that allows better and more portable arguments passing.
Good luck.

It looks like opencmd.bat is being executed, so assuming your PowerShell script works, is it possible you don't have administrative privileges?
You can also do it elegantly using JNA, I think this would be the target. But if you are rushed for time, don't bother.

Java programme works perfectly in NetBeans, but exits unexpectedly when trying to run

I've run into a weird problem today. I'll try to describe the steps I'm making as detailed as possible.
I've created a Java application in NetBeans. The application runs without exceptions when running within NetBeans by clicking Run Main Project. The total duration of a complete run is about 1min.
When building the project I see the following option in the output window of NetBeans:
To run this application from the command line without Ant, try:
java -jar "C:\java_libraries\PrxJobCommunicator\dist\PrxJobCommunicator.jar"
So i open the command prompt (Windows 7), enter this command + supply a mandatory integer argument and press enter
The application starts running, runs for a couple of seconds and exits without any message whatsoever.
the application writes to a text file at different points in the code, so I'm able to trace the output up to the point when it stops running. I've deliberately put some extra calls to the file writer method in order to find where the programme continues/exits but to no avail. Seemingly the programme simply stops running on a certain line and that's it.
I really don't know what the problem can be: the application runs fine in NetBeans and fails without any message whatsoever when starting from the command line.
Shall I check anything special in NetBeans? Do you know of any special technique to debug a jar file if it's started from the command line?
Any clues are welcome.
Thanks, Andras

I suspect that there is a difference in the classpath when the app is run from NetBeans, and when it is run from the command line.
There must be some kind of exception that is being thrown, have you got an outermost
catch (Exception ) block in the main method?
You could try to debug the application using "remote debugging", although you won't be debugging over a network, you can still use this method to catch the breakpoint started at the command line in NetBeans.
Here's an article that explains how to do remote debugging with NetBeans http://manikandanmv.wordpress.com/2009/09/24/debugging-java-applications-with-netbeans/

Netbeans by default uses your project folder as the working folder. It means when you run your program from console you have to CD C:\java_libraries\PrxJobCommunicator
then run java -jar "C:\java_libraries\PrxJobCommunicator\dist\PrxJobCommunicator.jar"
If above fails check the java version used in your command prompt. java -version
It has to be same as the one used by netbeans.
Finally the library path. Are all the dependent jars placed in the dist folder?

JVM Launched via CreateProcess() Loses Classpath Library

I launch the following command line (process) from a Windows VC++ 6 program using CreateProcess (or _spawnv()):
java -cp c:\dir\updates.jar;c:\dir\main.jar Main
and class updates in updates.jar (overiding some in main.jar) are not read or found. It is as if the updates.jar library cannot be found or read.
If I launch the same line from a shortcut, or from the command line proper, everything IS found and executes properly.
If I launch a JVM from the command line, keep it running, AND THEN launch the executable stub (above), then everything works OK also. (This makes it look like the issue is a file rights thing).
Any insight would be greatly appreciated!
--Edward

Try using Microsoft's FileMon utility to figure out what's happening. Set the include filter to "updates" to focus in on the problem.
http://technet.microsoft.com/en-us/sysinternals/bb896642.aspx

Have you tried this on another machine? Another OS? Which JVM are you using? Have you tried different JVMs?
Can you provide us with a minimal example which demonstrates the problem?

Thanks jdigital!
I tried FileMon and it showed me what I was doing wrong. The executable calling CreateProcess() had an unclosed file handle to updates.jar from an attempt to copy the update JAR earlier. Bad code that works in the production environment, but not in the test environment.