[xigency]

That has never been my impression. Java applications have a Java look.

What has actually impressed me as an easy way to do native looking UIs, albeit simple ones, is PyTK. On Windows, you can even select between the different styles that are internal.

[saagarjha]

Java applications use the look that the system provides.

[floatboth]

That is, Swing has some mediocre Mac and Windows themes. JavaFX comes with only a custom design.