Notions de base de Java

La réponse simple est "parce que".

Cela fait partie des spécifications du langage Java (en fait de Oak, ça prédate la sortie officielle de Java)

Citation:

Envoyé par http://www.javaspecialists.eu/archive/Issue055.html

Why is each public class in a separate file? (Section 1)

This is a question that I have frequently been asked during my courses. Up to now I have not had a good answer to this question. In section 1, we read: "Although each Oak compilation unit can contain multiple classes or interfaces, at most one class or interface per compilation unit can be public".

In the sidebar it explains why: "This restriction is not yet enforced by the compiler, although it's necessary for efficient package importation"

It's pretty obvious - like most things are once you know the design reasons - the compiler would have to make an additional pass through all the compilation units (.java files) to figure out what classes were where, and that would make the compilation even slower.

Et la vraie raison, c'est parce qu'à l’époque, c’était plus rapide de compiler un programme ainsi. Pre-1995, avoir une compilation rapide c’était du luxe.

Et ce qui en découle aussi : quoi qu'en disent les gens qui font du C++ ou du C#, c'est plus clair et mieux organisé ainsi.