Java 2D text API requirements exceed the capabilities of core X11 protocol.
Gnome/GTK desktop apps faced the same problem.
ie Java 2D and GTK apps share in common that they use client-side fonts
and want to support (eg) anti-aliased text on remote X11 displays, but
core X11 protocol doesn't support compositing.
The GTK solution has been to adopt the XRender extension.
This extension is in practice "new", as its only available on recent
X11 distributions. GTK is co-shipping with those releases so could adopt
it in sync. New releases of JDK for Solaris and Linux can now expect to
be deployed into that same environment so can also start gt leverage this.

In this RFE Xrender is being proposed to be used for text rendering,
when a faster solution (eg OpenGL) is not available.

Xrender potentially could be used for bitmap text as well as A-A text
and/or used for A-A text locally as well as remotely. What exactly is
selected will depend on the observed performance. ie its reasonable
to suppose that it would be faster for AA text over remote X11 but
its not clear it would be faster locally than using shared memory.

Additionally if other compositing operations are being used over remote
X11 it may be in that case there's no advantage to be gained from Xrender.