为什么Scala从对象的main方法而不是类的static main方法开始？

Question

In Java, a program starts from a class's static main method. But in Scala, it starts from a object's main method.

Does anyone know the rationality of designing like this?

Scala also provide a trait called App , which can replace main method if an object extends this trait. Does anyone have ideas about which one ( App or main ) is the preferred way?

Thanks!

Answer 1

Scala has singleton objects instead of java static members. So main method of object is analogue of java static main method.

Answer 2

I always extend App in my main class, and know of no reason why anyone would want to write an explicit main method -- except possibly to be compatible with some other code that was overly fussy about such things. Whenever I see an explicit main method in Scala, I wonder whether the code is very old (predating the App trait) or the author was new to Scala.

But this question appears to largely be about why the designers of Scala omitted static methods. You may find this question about how static members are not object-oriented helpful.

Answer 3

Scala doesn't have static methods. If Scala required starting programs from a static main method, then you could never run a Scala program, because you couldn't write a static main method.

Answer 4

Using static is like using global functions. Scala is pure object oriented language and has no statics. But in fact Scala compiler generates static main for JVM. It is recommended to use 'App' trait for short study programs.