Users on macOS with multiple monitors may run into the following error when using Java 1.6: 

java.lang.ArrayIndexOutOfBoundsException: 1
   at apple.awt.CWindow.displayChanged(CWindow.java:924)
   at apple.awt.EventFactoryProxy$2.run(EventFactoryProxy.java:92)
   at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:715)
   at java.awt.EventQueue.access$400(EventQueue.java:82)
   ...

The solution is to upgrade to use Java 7. The recommendation is to install the macOS installer that includes Java 7.