Jar file won't run with SWT Mac

Question

I executed into a jar file on MacOS. When running through terminal I get the following:

Joshs-MacBook-Pro:Desktop josh$ java -jar Untitled.jar
***WARNING: Display must be created on main thread due to Cocoa restrictions. Use vmarg -XstartOnFirstThread
org.eclipse.swt.SWTException: Invalid thread access
    at org.eclipse.swt.SWT.error(SWT.java:4711)
    at org.eclipse.swt.SWT.error(SWT.java:4626)
    at org.eclipse.swt.SWT.error(SWT.java:4597)
    at org.eclipse.swt.widgets.Display.error(Display.java:1112)
    at org.eclipse.swt.widgets.Display.createDisplay(Display.java:853)
    at org.eclipse.swt.widgets.Display.create(Display.java:837)
    at org.eclipse.swt.graphics.Device.<init>(Device.java:132)
    at org.eclipse.swt.widgets.Display.<init>(Display.java:736)
    at org.eclipse.swt.widgets.Display.<init>(Display.java:727)
    at org.eclipse.swt.widgets.Display.getDefault(Display.java:1446)
    at Login.open(Login.java:39)
    at Login.main(Login.java:29)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:61)

Answer 1

What is the question here?

• Is this a bug? > Probably not
• Do you have to create a SWT display in the main thread? > Probably yes
• Do we need some code to see what you are doing? > Definitly yes

Answer 2

As the warning message said you must specify the -XstartOnFirstThread flag on the java command when running SWT on macOS.

java -XstartOnFirstThread -jar Untitled.jar