Why main method is static in java [duplicate]

Question

I have heard some people saying " if main is not static then JVM could create an object of class containing main and call that main through object.
But the problem is how JVM knows which constructor to call in case of overloaded constructors or even if there is only one paramaterized constructor, then what to pass."

Is that the correct reason?
Because how can object of class be created without entering into main function?
Please give your views on this. If that is not the right reason, then what's the correct reason?

Answer 1

It's just a convention. The Java language designers could have easily decided that you must designate a class to be instantiated, making its constructor the main method. But calling a static method is just as effective and doesn't require a class to be instantiated first.

Also, if the class has a superclass, you could alter the behavior of program startup by changing a superclass (since superclass constructors must be called before subclasses), perhaps unintentionally. Static methods don't have this problem.

The main method is static because it keeps things simpler, but if they wanted to make it more complicated, they could have.

Answer 2

"Is this reason correct?"

It is at some degree, although it was never specifically explained like that.

We could have the convention to also invoke the constructor with String...args , that would imply you need at least an object to run, but ( probably ) the designers thought that wasn't needed.

For instance, there is no technical impediment to have something like this:

 class Hello {
       public void main(String...args){
           System.out.println("Hello, world");

       }
 }

As a metter of fact, Java creates a no-arg constructor for you if you don't specify one, it would be very easy to include a var args constructor too, if the class contained a main method, and create under the hood the following code:

 class Hello {
      // created by the compiler
      public Hello(){}
      public Hello( String ... args ) {
          this();
          main( args );
      }
      // end of code created by the compiler
      public void main( String ... args ) {
           System.out.println("Hello, world!");
      }
  }

But that would create unneeded code, and extra allocated object that in this case wouldn't do anything; two constructors ( instead of one ) etc. At the end it would look like just too much magic.

Is up to the language designers. In this case they probably thought it would be simpler not to do it and just validate if the invoked class had the special signature of a method called public static void main( String [] args )

BTW you can have a Hello! world program in Java without main method, but it throws java.lang.NoSuchMethodError: main

public class WithoutMain {
    static {
        System.out.println("Look ma, no main!!");
        System.exit(0);
    }
}

$ java WithoutMain
Look ma, no main!!

I know it is not an alternative, but yet, it is interesting isn't?