I came across this problem when updating jdk via brew. Somehow brew removed openjdk-12 and replaced it with 14. Pesky.
After some checks, I figured the Eclipse 2020-06 executable was relying on a hardcoded openjdk path.
To rectify this, I’ve done the following:
- Determine the jvm available on osx by dropping to command line and running ‘/usr/libexec/jvm_home -V’
Below is a screen capture of the available openjdks on my OSX. (openjdk-12 was removed somehow). Remember the location of the openjdk directory you wish to use.

2. Edit the openjdk path in eclipse.ini. The path to eclipse.ini is as follows:

Note: I have mine in $HOME/eclipse/java-2020-06. Yours could be in the Applications directory (ie /Applications/Eclipse)
Run ‘nano eclipse’
3. To get this:

4. Amend the folder name to the openjdk directory that you’ve determined in Step 1.

5. Ready to start Eclipse by running the eclipse executable.