Why is main not a key word?

[Sandra Dakurah]

Hi everybody,

I just started studying for the java 2 programmers exam. Can anybody tell me why main is not a key word? Can I use main for any variable or function name? (I hope not).

Sandra

[Stan James]

Well, give it a try. I'm reminded by the compiler every once in a while that I can't use "return" as a variable name.

In fact, main() is a method like any other. The *only* special thing about it is that when you give a class name at JVM startup the JVM calls the main method on that class with an array of strings.

The Java In General forums are good place for general questions ... this one is focused on servlets.

Cheers!

[Mark Spritzler]

Moving to the SCJP forum.

This forum is for Servlets questions.

Thanks

Mark

[marc weber]

A main method has "special meaning" (it can be used as an entry point) only if it is public and static, returns void, and takes a String array as its argument. That is...

public static void main(String[] args){}

As an entry point, main can also be modified with synchronized, strictfp, or final. Note that the String array can be labeled with any legal identifier, and this variable is local to the method, so you can define String[] args (or whatever you want to call it) outside of main as well. But "main" itself is not a keyword, so it can be used as an identifier of anything you like.

(Note that prior to 1.4, the entry-point main was not required to be public.)
[ December 01, 2004: Message edited by: marc weber ]

[marc weber]

Below is some illustrative (although generally inadvisable) code...

class First{
  //array with same name as main arg...
  String[] fred = {"One", "Two", "Three"};
 
  //entry main...
  public static strictfp void main(String[] fred){
    First fir = new First();
    System.out.println("local fred.length: " + fred.length);
    System.out.println("instance fir.fred[2]: " + fir.fred[2]);
 
    //calling non-entry main...
    System.out.println(fir.main(fred, 7));
 
    Second sec = new Second();
 
    //here main is a String...
    System.out.println(sec.main);
  }
 
  //overloaded non-entry main...
  public static String main(String[] args, int x){
    System.out.println("passed args.length: " + args.length);
    return "This main isn't an entry point.";
  }
}
 
//class using main to identify String...
class Second{
  String main = "This String is called main.";
}

Yes, this compiles and runs.
[ December 01, 2004: Message edited by: marc weber ]