_ is not on the classpath of project _, only syntax errors are reported

Every time I try to create a package for my java classes so I can finish my projects for school, errors like this occur:

When I finally try to run the program, I get an even more infuriating message:

It hurts me to be unable to properly test my code, even if I know I did well. It has been giving me anxiety for quite a while now, so I'm quite surprised this has slipped under the radar for so long.

• Operating System:
  

• JDK version: 15.0.2

• Visual Studio Code version:
  

• Java extension version:
  
  

Steps To Reproduce

1. Create a java class with methods and everything.
2. Put it in a folder with a test program.
3. List the folder as a package in both programs.
4. Try to use the class and it's methods in the test program. Both errors should be clearly visible by now.

Here is my code as an example of what can cause it. Try compiling either Test.java or Customer.java and it should be quite apparent.
Chapter10.zip

Current Result

A warning that constantly results in weird compiler errors

Expected Result

A working class that I can use

Bắt đầu bằng cách mở Chapter10.zip đính kèm và tái hiện báo cáo bằng Test.java và Customer.java trong VS Code sử dụng JDK 15.0.2. Kiểm tra cách tiện ích mở rộng Java xử lý thiết lập package và classpath. Công việc được xem là hoàn tất khi cảnh báo classpath được giải quyết và các lớp ví dụ biên dịch, chạy đúng như mong đợi.