In the actual development process, we may need to change the JDK version for the project. However, after the replacement will be an error, as follows:
Java compiler level does not match the version of the installed Java project facet.
Workaround:
First step: Set up the Eclipse JDK version
Windows---->preferences---->java---->installed JREs
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Step two: Set the JDK build version
Windows---->preferences---->java---->compiler
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Step Three: Right-click the project and set the JDK version to the above unified
Right-click the project---->properties---->java Compiler
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Error after eclipse changes JDK version