Java compiler level does not match the version of the installed Java project facet.
Unknown Faceted Project Problem (Java Version Mismatch)
1、preferences > java > Installed JRES > 选择java version
2、右键项目 -> properties > MyEclipse > Project Facet > java select version
3、右键项目 -> properties > Java Compiler > 选中Enable project specific settings > Compiler compilance level
三个统一则不会报错 文档为图文说明
