I want to write a class with three int values in them and manipulate them in main();

There are two ways I can think of doing this 

1. Have a seperate .class file and include it into another class file containint the main() function

stuff.java:

```
class stuff { ... }

class app {

public static void main(String[] arguments) {
   .. // manipulate the instance variables
     }
}

```

2 have the class and then a class containint the main function in the same file app.java

app.java:

```
class stuff { ... }

class app {

public static void main(String[] arguments) {
   .. // manipulate the instance variables
     }
}

```

Are these the main ways it is done in java ( I didn't see anything on including java classes ). Or can I make the stuff class contain main itself?