Compiling Java in Cmd and Running it

When I try to run compiled .class java program with this command

java main.class

I get this error

Error: Could not find or load main class main.class

When I compile the program with

javac main.java

It compiles nicely with no errors and gives me a .class file

What am I doing wrong?

I tried editing system variables to no avail.

You may simply write this to run the program:-

java main

Remove the .class