The error should be "“Source folder is not a Java project”".

Check the content of your .project and .classpath.

You can modify the .project to add the org.eclipse.jdt.core.javanature manually.
(But adding the java facet should be the recommended way)

The error should be "“Source folder is not a Java project”".

Check the content of your .project and .classpath.

You can modify the .project to add the org.eclipse.jdt.core.javanature manually.
(But adding the java facet should be the recommended way)

• regarding the lack of Java facet, make sure your Eclipse has the right Java version support, as described here.
• a .project and .classpath can be manually generated or copied from another simple Java Eclispe project.