The Eclipse project has a red exclamation mark

Cause: the package path pointed to by classpath in the project is incorrect.

[Solution]: Right-click the project name buildpath ---> Configure build paht..., and find the package whose Red Cross number appears in libraries as the path error. Modify the current path of the corresponding package in classpath. Then return to the eclipse F5 to refresh the project.

 

The following two paragraphs refer to the references I found online when solving this problem:

You use myeclipse to create a web project. A. classpath configuration file is generated under the project directory,
It is the configuration of jar referenced in your project. This. classpath has no impact on your web project
It is actually identified by myeclipse. This is because the. classpath file contains
The configuration references a jar, but in fact your lib does not contain this jar, so there will be a red prompt.
You don't need to find the. classpath file and your jar files one by one. Now you open myeclipse
Right-click your web project and find build path> Configure build paht...
> You can find libraries on several tabs. What you see here is the reference in your project
For all the jar files, see if there is a small yellow exclamation point on a jar icon?
If yes, select the jar and click Remove> OK on the right.
Wait a few seconds. Is the red XX on the WEB Project missing now? haha.
Explanation: the yellow exclamation point jar indicates that the. classpath configuration file references jar,
But this jar does not exist in Lib.