Why does the main function in Java reside in a class?

Question

I just started studying Java. And the main function of the program always resides in a class.

public class t{
  public static void main(String[] args){
  // do stuff
  }
}

I have studied C++, and in there the main function doesn't need to be in a class. Why in Java we have to do that?

Why can't the main function exist in Java without a class, like it does in C++?

Answer 1

Probably for the same reason you put question marks at the end of a question: that's just how they decided it's done.

The main method is the result of a convention that says "this is how the entry point's method signature should look" which doesn't exempt it from language semantics.

Java does not support methods outside of classes/interfaces and as such it has to be contained in one.

Answer 2

The "every method in Java must be in a class because the spec says so" answer is only part of the story. By having main() inside a class it is possible to have multiple entry points within a project. i.e. multiple classes with main() methods. This allows you to select a different main class at runtime rather than compile time. e.g.

java -cp program.jar com.example.Class1

or then if you want to run a different main from the same jar

java -cp program.jar com.example.Class2