Eclipse's ultimate solution for not automatically compiling Java files _java

My eclipse has been so silly lately that there are always a lot of projects, and startup projects don't have startup classes. Check the project generated in the class file, I am not even, or the former. It turns out eclipse was stupid, and it didn't help me compile Java files automatically. This is usually a few steps below. However, it is not automatically compiled.

The most basic solution--that's the premise.

Then clean and refresh the item below. If this is still not the case, use the following method, the ultimate solution ...

1: Remove the classpath of the JRE in the project

2: Add the JRE package to the Classpath

OK, that's it! Again, eclipse cannot be automatically compiled.