Install Eclipse JDT on top of CDT

I have the eclipse CDT installed, and I would like to install Java development functionality (JDT) on top of my CDT installation. I've been Googling from an hour but I can't figure out how to do this.

What plugin do I need to install? What update site do I need to use?

All versions of Eclipse have a standard base, then a specific set of plugins, depending on the version. All you have to do is go to the Help > Install New Software menu, select the Eclipse update site (e.g. "Galileo - http://download.eclipse.org/releases/galileo";), and under the Programming Languages section, select Eclipse Java Development Tools.

If you don't see the Java Development Tools in the list, click on the "already installed" link on the install page--you may already have the Java tools installed.

Remember to write http:// before the download.eclipse..... if you don't put that it won't work

For Eclipse 2020-06 the weakest precondition seems to be

1.) JDK 11

2.) eclipse.ini has top entries

-vm
<jdk-11/jre-11 path>/bin

3.) JDT appears in "Install New Software" repository http://download.eclipse.org/releases/2020-06 as "Eclipse Java Development Tools"

NOTE: Installation of Java 11 is not required, downloading/extracting ZIP File is sufficient, e.g. if you prefer to continue development with Java 8

Update for Eclipse Release 2021-3

Here, with the JDT-Release JDK 11 or later is already installed

• Choose Menu Help->Install New Software,
• Select Work With: "2021-03 - http://download.eclipse.org/releases/2021-03"
• Filter "Development Tools"
• Select "C/C++ Development Tools SDK"
• Complete Installation with Next ... Restart Eclipse