Eclipse sometimes reports that the compiler version does not match the JRE version, which is mainly related to two areas,
1, right-click on the project, then select the Properties option, then open the window to find the Java compiler option, set the version you want to agree
2, it is still right-click on the project, and then check the properties this option, then open the window to find the project facets this tab, open the window after the version number of the individual files listed
In Eclipse, when setting the version number of Web. XML, sometimes it is not possible to succeed with step 2 above you need to manually go to the local open project directory to locate the. Settings folder, and then locate the org.eclipse.wst.common.project.facet.c in the folder. Ore.xml file, find Jst.web to change the later version number
Settings for version numbers in Java