Can you run "java -version" from the terminal and post the output here?

[deleted comment]

Sure. 

The command java -version runs the JDK by default. 

This shows the JDK, I have a few installed.  7u51 is active. 

bash-3.2# pwd
/Library/Java/JavaVirtualMachines
bash-3.2# ls -Al
total 0
drwxr-xr-x  3 root  wheel  102 17 Sep  2013 jdk1.7.0_40.jdk
drwxr-xr-x  3 root  wheel  102 20 Oct 20:40 jdk1.7.0_45.jdk
drwxr-xr-x  3 root  wheel  102 15 Jan 10:20 jdk1.7.0_51.jdk

bash-3.2# java -version
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)



This shows the JRE location and version. 

dori:~ $ /Library/Internet\ 
Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/bin/java -version
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)


I suspect..  However the ganttproject is bundled to make ".app" executable.  
This process is what is requiring the old apple java 1.6. 

Same for Windows 7 with Java 1.7

"This Application requires a Java Runtime Environment 1.6.0"

 I reclassified this as a defect. It appears that Java launcher which sits inside our .app is pretty rusty.

As a workaround, those who have 'java' in the command line may use ZIP 
distribution. Or really install Java 6 (not sure if they can live together on 
the same system)

Hey Mac OSX guys, may I ask you to test this build with Java 7? ZIP file is 
available here, it contains GanttProject.app only. 
https://dl.dropboxusercontent.com/u/5454466/GanttProject.zip

Hey.   The build mentioned in #6 does not work for me.  

wildph$ open GanttProject.app
LSOpenURLsWithRole() failed with error -10810 for the file 
/Users/wildph/Desktop/GanttProject.app.

My Setup:  OSX Mavericks 10.9.2,    Oracle JRE + JDK 7u51 installed. 

[JRE] 
wildph$ /usr/libexec/java_home 
/Library/Java/JavaVirtualMachines/jdk1.7.0_51.jdk/Contents/Home

wildph$ 
/Library/Java/JavaVirtualMachines/jdk1.7.0_51.jdk/Contents/Home/bin/java 
-version
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)

[JDK]
wildph$ which java
/usr/bin/java

wildph$ java -version
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)

solved it.  the .app is launching now.  

Desktop wildph$ chmod a+x GanttProject.app/Contents/MacOS/JavaAppLauncher 
Desktop wildph$ open GanttProject.app

And Gantt Project reports it is running under java 1.7.51. 

Yes, it seems that I forgot to set executable bit on launcher. Cool, thanks!

Dmitry, I can give a fuller report now i've had a little time to play: 

with the executable bit applied, the new .app works - doubleclicking starts the 
GP application, using the installed JRE (java from 
/Library/Java/JavaVirtualMachines)

The application behaves normally.  I can open/close/save files, manage content. 
And printing works as expected. 

However...   

I can not open a file "with" ganttproject.app.   eg.   If i doublecick 
'file.gan' and choose to open with Ganttproject.app, this does not work.    GP 
starts up but does not open the file. 

workaround:  I need to choose to open the file using the Project > Open menu 
item. 

Regards, 

Graeme

Thanks for reporting!

brew cask install java

bogon:Users stonechen$ cd /Applications

bogon:Applications stonechen$ java --version
openjdk 12.0.1 2019-04-16
OpenJDK Runtime Environment (build 12.0.1+12)
OpenJDK 64-Bit Server VM (build 12.0.1+12, mixed mode, sharing)

bogon:Applications stonechen$ chmod a+x GanttProject.app/Contents/MacOS/JavaAppLauncher
bogon:Applications stonechen$ open GanttProject.app

Unable to load Java Runtime Environment.