title: Migrate to new eclipse version on Mac gives No class found error
body: <p>I upgraded to the newest Mac Pro running Big Sur (11.4) from my 12 year old Mac Pro running Mojave (10.14.6). The old version of Eclipse was version was Kepler service release 2. When I installed the Mac and restored from backup, Eclipse flat out would not run, so I deleted it and downloaded and installed the latest version 2021-03 (4.19.0). I also updated JAVA SE to version 16.0.1 from Java version SE 7.</p>
  <p>When I tried to run/compile a previous working project, I get:
  <a href="https://i.stack.imgur.com/9riaq.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9riaq.jpg" alt="enter image description here" /></a></p>
  <p>I then decided to update the libraries found in the Java Build Path properties to the latest I could find:
  <a href="https://i.stack.imgur.com/EAJbd.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EAJbd.jpg" alt="enter image description here" /></a></p>
  <p>to see if that made any difference. It didn't. I'm probably missing something very basic but I don't know what, since I use Eclipse only rarely.</p>