OpenJDK 9 has not been released yet and it is based on a development branch of OpenJDK, thus only use it if you know what you are doing. The official OpenJDK is 8. I highly recommend you to uninstall OpenJDK 9 and keep using OpenJDK 8.
With that out of the way, did forcing your system to use OpenJDK 8 through the alternatives systems fix your issue accessing /dev/ttyACM0? If you are still having problems accessing /dev/ttyACM0 please detach and attach your Arduino and then run $ dmesg $ ls -l /dev/ttyACM* /dev/ttyUSB* $ groups Look for USB messages right at the bottom of dmesg, they should indicate if your Arduino was recognized and what device was associated to it. The ls command will show you what user and group are associated with the device (probably root/dialout) and groups will show you what groups you belong to. In case you are not in the right group, please run $ sudo usermod -a -G dialout <your username> You need to logout and login again after adding yourself to a new group. If you need help, please copy and paste the outputs here so I can take a look. As an example, here is a dmesg output snip right after I plug an Arduino: [75244.850166] usb 1-3: new full-speed USB device number 50 using xhci_hcd [75244.978703] usb 1-3: New USB device found, idVendor=067b, idProduct=2303 [75244.978706] usb 1-3: New USB device strings: Mfr=1, Product=2, SerialNumber=0 [75244.978708] usb 1-3: Product: USB-Serial Controller D [75244.978710] usb 1-3: Manufacturer: Prolific Technology Inc. [75245.998601] usbcore: registered new interface driver usbserial [75245.998620] usbcore: registered new interface driver usbserial_generic [75245.998636] usbserial: USB Serial support registered for generic [75246.000675] usbcore: registered new interface driver pl2303 [75246.000698] usbserial: USB Serial support registered for pl2303 [75246.000721] pl2303 1-3:1.0: pl2303 converter detected [75246.001445] usb 1-3: pl2303 converter now attached to ttyUSB0 The last message indicates it has been associated to /dev/ttyUSB0. The ls command shows $ ls -l /dev/ttyUSB0 crw-rw---- 1 root dialout 188, 0 May 11 10:38 /dev/ttyUSB0 And my permissions don't include dialout access (I'm not in the dialout group): $ groups tdaitx adm cdrom sudo dip plugdev netdev libvirtd lpadmin sambashare vnstat sbuild lxd -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1579781 Title: librxtx-java fails to open /dev/ttyACM0 port! To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openjdk-9/+bug/1579781/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
