Java compiler level does not match the version of the installed Java project facet in eclipse

Symptom: The project icon reports the error "Java compiler level does not match the version of the installed Java project facet .".
Cause Analysis: According to the literal meaning of the error message, the Java version settings are inconsistent. This Java version is related to project installation.

Solution:

Since it is a problem with the project, it is natural to start with the project attributes. It's actually very simple,

Right-click the project "properties" and click "project facets" on the left side of the displayed "properties" window to open the "Project facets" page.

In the "Java" drop-down list on the page, select "5.0"

As shown in:

"OK"

Solve the problem.

Cause: it is because JDK of different versions is switched.