My understanding was that 20-12 would recognise Java 15 and 21-03 would recognise Java 16.

20-12 recognizes Java 15. You will need to install Java 16 support from marketplace on top of 21-03 to recognize Java 16.

> I appreciate 21-03 is still under development but I thought this functionality was already available.

Continuing from above, Java 16 is developed as a separate branch BETA_JAVA16 and is still under development. If you want to try this out you can update to Y build [https://download.eclipse.org/eclipse/updates/4.19-Y-builds/]. However, *repeat* this is *not* production code - still under development.

>Java 16 is not selectable as a compliance level in Eclipse.
For the reasons stated above, no - it is not yet available.

> Java 15 is ok but it is not compatible with source code from Java 14 with preview features enabled.
preview features are always tied to a particular release and compatibility is not guaranteed as per java documentation

>Derived objects which extend Java Objects do not have access to the parent variables. I believe this java behaviour is related JEP305 Pattern matching but was supposed to be fixed in Java16; hence my interest in using Java 16.

Please file bugs against Eclipse JDT Core for these -
we will analyze them.[https://bugs.eclipse.org/bugs/enter_bug.cgi?product=JDT]

I give below 2 examples of pattern matching and the errors. The Button is an object which extends JButton but is not recognised. It had no problem in Java 14 with preview features enabled.

if ((c1 instanceof Button b) && (c1.getName() == "close")) {

if (tmpObject instanceof Button b) {
if (b.getText().contains("close"){

> I would appreciate hearing about your experience, in particular how to get Java 16 recognised by Eclipse. I cannot find any plugins although I have installed https://download.eclipse.org/eclipse/updates/4.19-P-builds