Error: cannot find or load main class XXXX

error : Cannot find or load main class HelloWorld 

This is a basic problem , Beginners are easy to encounter this problem .

  Our code has been compiled , And you can see the same level directory , It has also been generated .class The file , Why execute under this path java HelloWorld Can't run this code ？

Correct operation method ： It should be src Run under directory , And write the package name and path .

In this way, the program code can run normally .