Eclipse has a red exclamation mark

General situation:
Right-click project name BuildPath---> Configure Build paht ... , and then there are several tabs above to find the package that appears in libraries with the Red Cross in the path error.

Modify the current path of the corresponding package into classpath. Then go back to Eclipse and F5 refresh the project. If you can't, try the Clean project. Project--->clean

If your eclipse project has a red exclamation mark, and there are no packages with red crosses in the libraries

   convert Eclipse to Markers view, Windows---->show view---->markers

You will find these error content,
Archive for Required library: ' XXXXXXXX001 ' on Project ' xxxxxxxxx ' cannot be read or was not a valid ZIP file
then , Open the. classpath file in the project root directory with Notepad and locate the "<classpathentry kind=" Lib "path=" XXXXXXXXX001 "/>" line, delete
Save, refresh, this error will not be, and thus the red exclamation mark is not.

Eclipse has a red exclamation mark