Question: I need to execute a method in `.java` or `.class` but this class doesn't have a `main` function (I can't use `main` function because it has no return value) I must execute this method in cmd , Is there any way to resolve this problem ?

Answer: 
First of all: Java has methods, not functions.

Up until Java 7, it was possible to run Java without a main method using the static block, but this was removed as of Java 7, because the static block was not supposed to use this way.

If you want to run it: add a main method.
If you want to call Java class from Python and get result from it, then you should use something like `JPype` or `Pyjnius`.

See [Calling Java from Python](https://stackoverflow.com/questions/3652554/calling-java-from-python)