I worked on a Java desktop app, that had a highly complex UI written in Swing, for ~14 years. We only officially targeted Windows as a platform. For a few yea

I worked on a Java desktop app, that had a highly complex UI written in Swing, for ~14 years. We only officially targeted Windows as a platform. For a few years I switched to a Linux development machine. The only code change required was for our third party license dongle - to reference the correct native library needed for machine fingerprinting. We also ran it on another developers Mac just to see if we could - again we only had to comment out the licensing code and it works flawlessly. So from that experience I would say Java definitely lived up to Write Once Run Everywhere. FWIW we used the Nimbus Look and Feel. Other LAFs may not have had as much polish applied.