It is bundled with Swing and AWT, but neither really looks like native, which has been a consistent complaint about them.

There is also JavaFX, but that is no longer bundled with the JDK.

Swing with the Nimbus Look and Feel isn't too bad for a quick, functionality-focused widget and it's super handy to have it still built into the JDK. It's not a good option for building a long term desktop application UI now though. There is no on-going development, the focus is now in Java FX. Prior to AI tooling, finding answers to Swing questions was getting much harder. Surprisingly I've found Claude to be pretty good at providing simple Swing UIs.