Solve the red exclamation mark of the eclipse Project

Cause: the red exclamation point is displayed because the jar package path is incorrect.

Solution: Right-click the projectBuild path->Configure build paht...(Or propertise-> JAVA build path), in Java build pathLibraries, The Red Cross is the package with the wrong path.

After processing, return to refresh the project. This problem is generally caused by importing other projects or some of the previous jar packages to move their storage locations.

PS: yellow shield exclamation point on the project, indicating that the jar package has been referenced, but this jar package is not actually used (it can be understood as a variable, but it has been used in the future)